I would recommend Lynn Radeka's masking kit. It comes with a punch for making alignment holes and an alignment contact printer for making masks, which is itself the negative carrier you use for printing. Just tape a strip of scrap negative to the extreme edge of the negative, punch alignment holes in the strip, and any masks you make are automatically aligned perfectly by punching them before contact printing to them. Plus unsharp masks only scratch the surface of what you can do with masks and the masking kit pretty well illustrates the options. There was a series of articles several years ago on these techniques, I think in Darkroom Techniques magazine.

I got interested in masking and attended his workshop and got an eye-opener in print control I didn’t know was possible! There are before/after comparisons on Radeka’s website.