I use overlays a lot. A LOT. That is the way I was taught. I can crank out a pretty good sketch without an overlay, but the only way I’m going to get a sketch better than good is to overlay. That Ferrari sketch I did in the doodles topic yesterday was 4 underlays.
I explore and think a lot on the page. I find that people who visual the design in their head and then sketch it don’t often move beyond the expected. And when you work in a team iterating in your head doesn’t cut it. You’ve got to show it. You never know what iteration will spark another idea for one of your team mates.