Stop in for a cup of coffee

One of the things I do as well on those is to elevate the part and do them vertical if you will so that I use gravity to help me with the debris that invariably enters openings, you may or may not be able to do this depending on where you are in assembly process. I scrape mine first with super sharp gasket removal tool. It is designed to do exactly that and works great. Then I do as @toolmanmike suggests and finish them off. I always and I mean always cover the openings. A small vacuum helps as well, I run it inside the openings to ensure I have no debris. Even if I can’t see any.