Brehs, how do y'all make your 3 rep max bench weight into weight you push for 8 reps x 4 sets?
You basically just asked how to get stronger. If you have a true 3RM and it later becomes a 8RM or more, you had to get a lot stronger.
1. Bulgarian Method for PL: read the ebook first. You basically will bench 1 rep sets and eventually add a couple doubles/triples after that. Assuming you don't snap your shyt up, eventually that old 3RM will become light work.
2. Increase TUT. Start doing forced reps, negatives, strip and drop sets, etc. The hypertrophy effect should allow you to eventually transmute this new size into greater strength.
3. Do a bench-specific program. By increasing your 1RM, all of you other RM's should theoretically go up as well.
4. Bulk. BP is really the only PL where extra weight (not muscle) will almost automatically translate into greater poundages moved. Squat and dead don't benefit nearly as much/at all.