1. You might try pre-drilling and slightly enlarging the holes in the FT with a bit that's just a little larger than the holes so the screws go in easier.
2. If you're going straight into plywood, you should be able to buy #4 screws that are shorter in length.
3. It's generally not necessary (nor desirable) to screw every piece of FT down, especially on straights. One section every 2-3 pieces should be enough.
4. Don't overtighten, especially switches.
