OK. So what I have done is shot a plate of a lit candle that is static and totally straight up and down. I'm applying that flame to footage where a character holds an unlit candle; however, the character moves the candle from left to right.
What I am looking for is a warp, corner pin, or slit scan expression of some kind that will skew the fire footage with the movement of the tracked candle. IE, if the unlit candle the character is holding moves left, the tracked fire footage will skew at the top of the flame to the right, etc.
I've done it by hand by animating a puppet tool, but it is extremely tedious and not as consistent as I need it to be.
I have very little knowledge of expressions, but I would imagine it is also possible to maybe place a null on the track at the bottom of the flame then another untracked null to the top of the flame that is parented to the bottom one. Then apply some kind of delay expression? then link it to the puppet tool?