I trained as an engineer. My speciality was design for production.
The secret to painting fast is to break things down into logical steps.Try to organise it so that you use each colour only once. (see above for Zulus)Try to organise it so that you do rough work first and cover mistakes with later steps.Paint in batches of 20-50 similar figures.Good light and a pair of reading glasses helps.Start with sprays, then ridiculously large brushes, then large brushes and only use small brushes for the final details.Most painters use very small brushes. This really slows you down. I actually use no 6 and number 4 brushes at first. Then no 2 for details and only move to no 0 for really tiny stuff.I also use washes or army painter for shading as it is much quicker than painting dark shade, main colour and highlight.
I regularly do 25 figures in a week and occasionally 50 or more.
I usually paint with brushes no bigger than 0, and often use 0/28 or 20, so yes it does slow down the process. I also paint with a wash technique - main paint, ink or thinned acrylic darker paint wash, and then highlight. I've tried the dark shade, main color and then highlight, which a good friend swears by, but I often dislike the results.
Guess I need some bigger brushes and keep the wash painting up. I also just picked up some Army Painter light and med shader dip, so hopefully my pace will pick up.
I guess part of my problem is that I only recently got back into painting after a 25 year absence, and 2 of my best friends are master painters of minis and they sort of intimidate me, so I try and match them, and end up not doing a very good job of it, just because I was near Master level myself (I used to belong to the Long Island Military Modelers Club, which was a painting club for historical, military and fantasy minis, and they held a huge contest every year with participants from all over the world). I guess I just hate to admit to being rust after all these years.