14 yrs ago, my 67,
Started with 80 grit, filled a couple dings, next 180 , then 320.
Worked that 320 for awhile,
2 wet coats DP 90 ppg epoxy,
2 coats of ppg base , 3 more ppg 3000 clear.
Still doing fine .
If you have drained the rear end , yes you use the 4oz bottle. put it in 1st before adding the 80/90 so you know you can get it in.
If you were just topping one off or had a little chatter to try to get rid of just a ounce or two.
check and make sure your striker and latch is not pulling it to one side more than the other,
also ck your front edge gap, if it seems tight on one side , loosen just that side that is close on the front and adjust it back a hair.
that will close up the gap some on the other side.