I agree - they can be a real PITA to bed.
I use the barrel (blue tape wrapped around it) and the tang with 3 layers of blue masking tape under it to hold the barreled action horizontally, and use blind screws (bolts with heads cut off) in the action screw locations (also with blue tape to fill the entire hole) to align vertically. I often try to be sure the forward hole's blind screw and tape fully fill the hole, while the rear one I may make a bit smaller so it doesn't bind. I say this as there are often times when the barrel and the two action screws don't perfectly line up, so the rear screw is allowed to be a tiny bit to one side.
Take it slow, that's always the best piece of advice.
Good luck!