make sure when setting the head on you don't drop it onto the gasket.

to clean the threads, not every one has a tap that long!!
so I use a brass brush for cleaning a 20 ga shot gun, or what ever you have that fits well.
then brake cleaner and compressed air using a tube that will extend the blower to the bottom of the hole, (cover with a paper towel so you don't get a shot of dirty brake cleaner in the face.
LIGHTLY oil the bolt hole and threads of the bolt. tighten, drive 200 miles or so and re check bolts and lifters.