Sure, when we did our HIV prevention research in Chicago, New York, and Durban South Africa, we hired knowledgeable people from the community and got the to understand what we were trying to accomplish and if they brought in they recruited. It was a win/win for everyone.

One needs to first assess what types of communication strategies hard to reach populations have access to on a regular basis.

Find out who are the gate keepers in the community. You can go through them and or also what kinds of networks do these hard to reach population have, then contact them use them for recruiting. Also you can find one of them and then use snow ball sampling.

Depending on what the target population is, Facebook Adds and Google Adds might work quite well. We did that for surveys on illegal drugs and had a reasonable amount of participants.

It depends on what you want to recruit for...Research, Recruitment into a nursing, or other health program? It may take face-to-face recruitment or use of well trusted community you build relationships with. I recruited for a nursing program so I had many strategies.

There are no easy answers to this in my experience with refugee communities.

I worked with a local clinic who have been there for nearly 10 years. The women I work with respect the clinic's incredible input into their community, and, as a result, are motivated to be part of their research projects.

One thing to note is that there is an increasing tendency to refer to these kinds of communities as 'less-often heard' instead of 'hard to reach'.

Good luck with your work!