After much trial and error, here is how I do it:

I don't use the diffuser anymore.

What I do is put product in my hair, let it air dry anywhere from 30 to 40 minutes then I use the attachement on the dryer that is for when you straighten your hair. On high speed, high heat I take cup sections of my hair and point the dryer at the roots and mostly the underside of my hair and I only do it for 3 to 5 minutes, though mostly it will take LESS than 5 minutes to do.

I never thought I would get good hair this way but I need to blow it dry for volume and curl definition. I HATE how it looks when I air dry - it's just too flat even though my hair is thick and coarse. The diffuser was taking too long so one day I didn't have the time to spare 10 freakin' minutes holding a diffuser in sections on low speed/low heat only to have it come out frizzy anyway because it was taking too long to dry and I was messing with it to much during the drying process with the diffuser.

This way, I mostly air dry, then blast it with the blow dryer and I am done in half the time with way better curls, since I am not messing with it as much. If I try to diffuse or blow dry right away I will ALWAYS, no matter what, get dry looking, frizzy, flat yucky hair. ALWAYS. And if I am stupid enough to blow dry right away I HAVE to blow dry it till it's bone dry or it REALLY looks horrible and that takes FOREVER and is not worth the effort! I came across letting it air dry first by accident and I never looked back.

Hope that helps!
HG: Biosilk Rock Hard Gelee (always and forever)
Cantu Naturals s & c (shampoo 1x a week), use conditioner as a co-wash every day and LI under my gel.

Air dry then diffuse canapy layers only for volume
Coconut oil before/after coloring grays and on ends.

2b/c mix waves/curls - coarse, frizz prone, med. thick, porous, at-home color, protein sensitive but I still need it sometimes, glycerin-sensitive (I think) in high humidity. After 16 years on I FINALLY figured it out..