i'm no professional myself but since no one responded yet i guess i can give it a go!
about the feeling it's so turning on, can't say it's pain free,specially using rough thin ropes, but the pleasure beats it in every tug on the rope!
when? well when i feel like it

in fact when i feel a bit kinky! but i don't use it all the time and/or just as a selfbondage
about how, well here is what i know and experienced so far !
_first tie a rope around ur waist and make it tight enough in place, not too much to hurt though. if someone is tying u it's highly recommended that he/she ties ur wrists behind u and tie them to the waist like what was said. then pass another rope over the rope in front part of the waist binding(or behind it .ur call)grab the ends of that rope and pass it through between ur legs and...u know make sure it runs over there, taking good place

then tug it from behind till it reaches the least press on there and pass the rope over the the waist rope at behind ur back.
for the rest if it's just the crotch rope and nothing more u can tie it there and u can have fun tugging on it time by time, which in this case i suggest passing the rope from behind and tie it in front of the waist binding .sounds easier to knot in front doesn't?!
if u like more challenge i suggest a hogtie. for this before the crotch rope tie ur ankles together. after passing the crotch rope from behind lay on ur belly and pull over ur tied feet then tug the ends of the crotch rope till the least pressure point and connect it to ur tied ankles...from now on with each struggle of ur feet it tugs the rope and ...well have fun with that
