You may have a harder time finding MHRB if you are in the US. I have looked and found some at high mark up and in 2011 prior to the crack down on the bark I had been ripped off for inactive material so I am wary of purchasing it after the ban. There is a lot of acacia confusa around if you want to look into that but it is a fatty plant and defatting is a must.
I cant comment further because i basically stopped after 2012 when the last supplier i was working close with got shut down, not arrested but inventory seized. I like working with the same people and having a lot of communication so once i lost that one i lost motivation as its not exactly easy to find supplies that will work with you at least in the manner i like to.
Good luck!