At this point, I'd suggest taking a break from boat building.

Proceeding in an impatient manner will result in your cutting corners, and building a boat that looks it. The whole building process takes time and patience. If you can't give it that time and patience today, then wait until tomorrow when you can. And sometimes that tomorrow isn't for another week or two or six.

Sanding down all the way through to wood isn't good. Those areas are now weaker for lack of fiberglass, and patching isn't a nice way to do things on a brand new boat. Slow down on your sanding, pay attention when you can see weave.

No, you don't absolutely need to get every square millimeter of the hull scuffed, though it helps. As much as I've used a power sander, I've used a hand block sander and my fingers. They work nicely in divits.