[Callers] language of calling

I'm compiling a list of uncommon and obscure contra dance moves for a choreography book that I'll publish in the spring. The list contains about 100 right now. The interesting thing is that many on the list are different calls for the same move (like Jersey twirl and Nevada twirl). I appreciate the precision of MWSD but also enjoy the looseness of the contra scene. I'd like to know how callers use the calls slide and shift. Are there situations where you're more inclined to use slide? How about shift? I think I see a pattern but it's not 100%: Slide- seems to be used by a number of callers usually in conjunction with a circle left to progress. Shift - seems to be used, for example, after a partner swing in order to progress. Tom