Dr. Bongi advice is very good.  I have worked with soil scientists and geologists for many years.  I have seen they learn to read landform and vegetation indicators from both detailed soil and substrate sampling, but also correlating their findings with remote sensing such as aerial photos.  Much surficial detail can also be obtained from LiDAR if that is available on example areas.  As suggested, if some lands are inaccessible, finding adjacent surrogates is appropriate.  I have seen much gained in reading the landforms and vegetation, and at times instream materials may be helpful too for particle sizes, are they warn and rounded by water tumbling, or sharp edged, etc.  I don't like heights or very steep terrain either, but there are mountain climbing equipment and other safety equipment available, or you may find individuals willing who enjoy mountain challenges for sampling or taking pictures or measurements.  On slopes over about 70-80%, a light weight but strong bamboo watking stick or similar help (ropes) is inexpensive but surprisingly helpful.  Anything over 90%, I would probably not try except for short distances or if the vegetation was strongly rooted - each individual must know their limits, safety is important.  Years back, we had a helicopter drop us off in some very remote country, and we just took our time to be careful to make it back safe, access what we could, and recognize what we could not.  Steep lands takes some getting used to, as I grew up in flat Nebraska, but learned to safely work in steep lands and landslides of N. W. California and S.W. Oregon.  Another point may be what do you expect to gain from accessing some of the steepest terrain and soils - is it important habitat, landform stability, need for road access or something else?

By an alternate location sample if a landscape map is available. The debris at hill slope bottom can be a useful indicator to find an analogue in road cuts or small steps wuth the same charateristics, as in https://pubs.usgs.gov/ds/801/downloads/Appendix%201_NASGLP-Soil-sampling-manual.pdf

Dr. Bongi advice is very good.  I have worked with soil scientists and geologists for many years.  I have seen they learn to read landform and vegetation indicators from both detailed soil and substrate sampling, but also correlating their findings with remote sensing such as aerial photos.  Much surficial detail can also be obtained from LiDAR if that is available on example areas.  As suggested, if some lands are inaccessible, finding adjacent surrogates is appropriate.  I have seen much gained in reading the landforms and vegetation, and at times instream materials may be helpful too for particle sizes, are they warn and rounded by water tumbling, or sharp edged, etc.  I don't like heights or very steep terrain either, but there are mountain climbing equipment and other safety equipment available, or you may find individuals willing who enjoy mountain challenges for sampling or taking pictures or measurements.  On slopes over about 70-80%, a light weight but strong bamboo watking stick or similar help (ropes) is inexpensive but surprisingly helpful.  Anything over 90%, I would probably not try except for short distances or if the vegetation was strongly rooted - each individual must know their limits, safety is important.  Years back, we had a helicopter drop us off in some very remote country, and we just took our time to be careful to make it back safe, access what we could, and recognize what we could not.  Steep lands takes some getting used to, as I grew up in flat Nebraska, but learned to safely work in steep lands and landslides of N. W. California and S.W. Oregon.  Another point may be what do you expect to gain from accessing some of the steepest terrain and soils - is it important habitat, landform stability, need for road access or something else?

Interesting question ...though you may find some peripheral information on earlier question discussed on RG given as below: 

https://www.researchgate.net/publication/222652164_Relationships_betw

Here are some PDFs , they could give some idea of how to approach this important but very practical issue...

Article Relationships between soil properties and slope position in ...

Thank you sir.

Application of geospatial tools is surely one option using grid soil sampling, but question is very good and practical. 

Dear Ranjan,

Interesting advises had been given you.  I think that you can estimate some attributes is you know parential material because you will know types of stones and it could say wich chemical element have. It could say you pH, presence of carbonates, etc.  It is also important to know wich indicator plants there are, and quantity of rainfall.

High slop are enthisol orden (USDA taxonomy), have some similar attributes.

Dear Ranjan,

I would suggest that the level of detail during investigation would be influenced by the end purpose of the sampling, and that the posts provided above cover the use of an alternative 'surrogate' location within an area of more suitable topography. However I would note some caution if using the information for an engineering purpose that although the soil/rock types present may be similar, the stratigraphy noticed can (and generally will) vary significantly between steep inclined areas and the adjacent flats.

If determining the soil stratigraphy of the inclined areas is necessary, or you require verification of the continuation of strata across the area, I would suggest performing a seismic reflection survey or similar prior to intrusive fieldwork if financially feasible. This survey would allow confidence when determining a suitable alternative sampling location to ensure that the required strata can be sampled.

i agree with Hansen