[T77911S]

don't use permatex or gasket sealer, you will regret it the next time you have them off.
I don't recommend a file on the covers.
I have these little round "fiber" disks, don't know what they are called but you can get them at harbor freight. I use them on a little air grinder form harbor freight, about $15. they clean the surface and make it look like new.
I also use a die on the studs to clean them up.

get the reusable valve cover gaskets. you will not regret it. very lightly snug the bolts. no gasket squeeze.

then check the cam line going to the cam tower. replace the washers. I think there are 3.
the oil will leak from there and run down and drip from the bolt and it looks like the stud is leaking.