Blame or credit Ollie Edwards.
This is how he shows tying off the hackle on a Klinkhammer in an article in FF&FT written many moons ago and so, knowing no better, I have always followed it, and it works!
Basically you tie in the hackle after the wing post, leave it pointing in the air, and then finish off all the rest of the fly and whip finish as normal, all with your usual tying thread. You then pick up your spool of spiderweb, catch it onto the wing material, build up a short post and then let the bobbin hang out of the way. Wind the hackle down from the top, catch and tie in with the spiderweb and then whip finish around the base of the hackle. Easier if you use a whip finish tool.
Edwards suggests rotating the fly in the vice downwards through 90 degrees so the wing post is horizontal for this part of the operation but I find it easier if I leave the fly in its original position in the vice.
I know there are other ways of tying off parachute hackles, but if Ollie Edwards says this is the best way, that is good enough for me.
Cheers
Irvine
PS I'm ham fisted too but its surprising how soon you get the feel of how hard you can pull.