Zmw- Good question. The answer is that it's optional. You will have a much smoother cleaner looking surface if you fill in the pits with an epoxy patch first, but if you don't, it's not going to cause a peel. The pits are caused by the rocks getting knocked out of the cement. It's a relatively easy and cheap fix, and will make a huge difference in the end result of your floor. Rustoleum makes a good patch as you noted. If you can't find it, then go with Sherwin Williams GP3500. It's a 2 part patch that comes in one Quart for Part A and one quart for Part B. Mix up just a little bit at a time, because it dries in minutes. After patching you can roll over it relatively quickly, usually in under an hour.
We have installed hundreds of garage floors, and every customer who has ever declined the patch work, has always regretted it after the epoxy has been applied because the pits stick out even more after the floor has been coated. After you apply the epoxy, it's a little too late to do patch work, unless of course you're willing to put down the money for another coat.
Therefore, I highly recommend filling in the pits.... otherwise, you will regret it.
Best Luck!
