As for selecting a sample, make sure your kick sample peaks at around 100 Hz and your snare sample at 200 Hz, that way both of them will have the typical fat DnB impact.
I can't really help you with that, but try to find some good DnB Sample CD's, it will make the processing a lot easier. The basis to good DnB are good samples, it's easy as that. Oof, you're not exactly picking an easy genre to get started with.
Wiesty, are you sure you are actually talking about DnB? Have you ever heard DnB? Why would you want to change the velocity note by note for a 'real' feel when you're aiming for electronic drums?
