I do things a little bit different, but that depends alot on the action that the one piece picitiny rail is being bedded to. On custom actions the one piece rail usually sits nice and flat on the reciever.
When doing remington recivers the rear reciver ring usually tails away on the rear right side, so if you dry fit the base you will notice a gap on the right rear where the base dosn't make contact, this can be measured with a fealer gauge for gap.
If you tighten down all four screw without a shim of either brass or epoxy you will just twist your rail to match the reciever. Then when you atatch your rings the rear ring will cant off to the right, causing a mis-alignment with the scope to reciever.
I dry fit the base and find the 2 screw holes that disrupt the base the least, one on the front ring and usuall the front rear ring mount hole.
I then prep the reciever and base, clean degrease, ect. Wax my screws and screw holes.
Epoxy the base and set it on the reciever. instal only the 2 screws in those holes that I predetermined will not twist the base. I snug them up just so they make firm contact but not tight enough to start twisting the rail.
Clean up the uze out and the unused reciever holes.
After 24 hours I remove the 2 screws used to hold the rail in place, clean and degrease the holes and screws and reinstall all 4 screws to the proper tourqe with blue lok tite.
I have removed some of the rails I installed this way years latter, when the screws are removed, the rail still holds fast and needs a couple of whacks from a mallet to pop the epoxy joint loose.
What this process eliminates is any twisting of the rail, or possibly the reciever if using a heavy steel picitiny rail.
I have also epoxy shimmed Tally one piece ring base sets, but because the front and rear sets are not conected it helps to cut a small brass shim for the rear ring base so that it does not cant to the right. The only difference is I use all four screws snugged up, Hear it is not neccesary for twisting just correcting the ring cant. Then when finished, as always lap the rings.
The remington high polished recievers, like the sendero, are the worst for this rear reciever ring right rear drop off. As they polish the reciever along it's length they reverse direction at the ends and this seems to work off a little more material in that area causing the dimensional problem.