I'm Scottish. Come from Aberdeen although I live in England now.
Best way I can help folk to pronounce the "ch" is to think how a cat hisses when it's angry.
The sound comes from the back of the throat so try hissing like a cat - making sure, of course, that there's no one else around when you do it or people could be giving you some very strange looks LOL.
Another way is a bit like gargling but without the sound. You gargle at the back of the throat. It's very similar. Takes a bit of practice.
My husband is English but he can pronounce the "ch" quite well now.
