A bold step to take! Wonderful...
Any chance we can get you to post a link(s) showing us the precise-specific techniques you are having trouble/problems with?
The body is connected, our parts are far more connected than most ever realize. The typical "butterfly" requires lower back & hip musculature "disengagement". Meaning, if they are tight, no matter what else your muscles, mechanics are doing correctly, if the hips, and back muscles are tight/normally contracted you will not
access the muscles you want to use in the butterfly.
Any chance you are rolling/rounding your shoulders, upper back rather than bending from the hip? Have you put firm cushions, pillows under your hips to raise them up 4-6 inches so you can
short-circuit, ignore the "problem area" for the immediate moment?
and explore their articles and video clips section of "asana". There is a style of Hatha-Yoga which is called "Iyengar Yoga" which is disparigingly called ~prop yoga~ by some. Sometimes different props can help you achieve the particular stretch(es) until your muscles let go, and uncontract back to their healthy, and proper state.
Guarantee the stretches shown below will get the muscles you are after, specifically the piriformis and IT (Ileotibial band) stretches in particular.http://endurancesports.com/itbs.asp
You cannot rush this, that is not how it works. No matter how hard you work, and try to "force" the issue (literally) will contract, and microtear your soft tissues even more. You have to give yourself the time to isolate the muscles you're after, identify them, and then slowly disengage the ones that don't need to be involved in whatever stretch/technique.
Rush this and you will get hurt... so do not!