Hi! I use acrylic (Apple Barrel and Folk Art brands) and enamel for metallic details (Testor and Model Master brands). For brushes, as tiny as I can get them; my current smallest brush is 3/0, and it's from a set of red sable brushes by Atlas Brush Co. (this is close to what I've got: link).
Customs vary! Simple repaints are usually no more than a day (2-4 hours), anything that involves having to work with props usually ends up taking 2-5 days depending on the complexity of the work and materials involved, but the yarn Yoshi took me weeks as it was extremely tedious and I had to take breaks.
I'm using an Atlas No. 68B Red Sable brush that I trimmed down even more so it's super tiny! It's one of these!