I was thinking about this myself recently. I have not done it yet but I think a good way is to purchase a roll of adheasive magnetic tape. You can stick that to the wall, then put on paper, then put other long strips of the magnetic tape or small neodymium magnets over it to hold it up.
easier, faster, and less messy than plain masking tape, and no need to nail long metal strips onto the wall. various vendors sell this tape, and its pretty cheap with various lengths available.
When I did this many years ago, I used masking tape. Blu-tac sounds like a good option, if you don't have a big vacuum board or magnet strip setup.
If you've got room for floor projection, the basic technique is to reverse the enlarger column and turn the enlarger around, weighting the baseboard, so the enlarger doesn't topple over. Some enlargers like Omega D's can do this easily. Some require unscrewing the column mount from the base and putting it back with the head facing the other way, and I suppose that for some enlargers, there may be no easy way of doing it.
I would think one of those cheap metal easels from Delta would be a good way to wall mount, They come with the magnetic strips to hold the paper. Since the easel is thin metal it shouldn't be to hard to mount to the wall. Robert
The side of a file cabinet (Black metal) and a few magnets would work! True up the file to match the enlarger and choose a suitable enlargement size it should weigh enough to keep it from moving accidentally. I've also found magnets that are the size of business cards (at Staples) that are covered on one side with an adhesive. Leave the protective cover on or stick some black paper on it. They are strong enough to hold down most papers, or cut them into strips to get more coverage! I also use them to hold down test strips when making prints on a regular metal easel. I get an unexposed paper white at the same time.