I was not able to consistently HQ twinthreads until I reached about 350craft/340control with about 317 CP (no food stats)

I am now able to pretty much 100% HQ from NQ at 362craft/348 control and 330CP (no food stats), if that gives you an idea of where you need to be.

HQ'ing 40/40 recipes is going to always be more difficult because you have to use manipulation after 2 touches, and hasty touch can still fail often even with SHII

Here are my cross class skills that I use..
Hasty Touch
Manipulation
Waste Not (rarely)
Tricks of trade (extremely useful)
Steady Hand II (most important)
Ingenuity
Innovation
Byregots Blessing (finish quality gambit)

I used to go with rumination and then -> manipulation/waste not -> ingenuity to finish synths, but byregots blessing is far superior