I'm doing a customer's quilt right now that will be shown in competition (hopefully)
I'm using invisible thread.
1) Superior threads has a new micro something thread --- it is NOT hard, it is pliable, soft and you can't tell it's there when you quilt with it. The old invisible thread was like using fishing line --- and would stick you.
2) LOOSEN both the top thread -- a lot! on my longarm I loosen it a LOT. And only use the thread on the top -- not in the bobbin
3) GO SLOW --- very slowly quilt ---- about half speed than you'd usually go.
It's worth it -- TRY it!!!
ON EDIT: Superior says you can iron this monofilament thread ----- I haven't tested that yet, but they've never steered me wrong yet.