Actually, I don't really have a "Nile" kick per se, because I used two very different ones on the two albums I did with them. I might have played samples for someone at some point, and told them that I used a particular sample for a Nile record, or something like that.
I generally just try out several different samples to see which fit the drum sound and the music best overall. For layering/treatments I use any number of things - either pasting in by hand, audio triggering, Drumagog, Sound Replacer etc - whichever works best, or should I say most effectively, and that will usually vary a lot depending on the sound/clarity of the original recorded drums.