RUSLE version 2 has subfactor method refer (RUSLE 2 manual)for estimating the variables involved.

For Instance, R factor can be estimated using pluviograph data with atleast 10 years of data.

K factor can be estimated through soil samples and analysis for physical and certain chemical properties, LS from DEM, C from landuse and P from Conservation measures adopted in the study area.

Somebody--can't remember his name unfortunately--did his PhD on the applicability of the USLE and/or RUSLE in South-Eastern Nigeria around 1986 with University of Ibadan and Dr Rattan Lal of IITA.