Re: case prep & use of Dillon 550
There are two distict cases here: Pistol and rifle.
For pistol rounds I do not clean the primer pockets. I never have in over 20 years of reloading on my Dillon. Some of the brass I reload is 20 years old and never had the primer pockets cleaned after many many reloadings.
Rifle brass is diferent. Rifle brass stretches and needs trimming after a couple of reloading (and some calibers after every reloading!). When I trim the rifle brass, I clean the primer pockets simply because I can. The sequence of events has to be to first size the cases and remove the primers, trim the brass, chamfer the case mouth, clean the primer pockets, and brush out the case throats.
There is no need for a seperate press to size the rifle brass before trimming. The Dillon RL550B cna be used as a single stage press or a turret press or a progressive press. To use it as a single stage press just slip the brass into the sizing station as you normally would do, pull the handle to size the brass and remove the primer (don't put in a new primer), rotate the table and remove the case from the second stage while you put in a new peice of brass in the first station. It is almost faster than using a single stage press. I then trim the brass and clean the case throat and primer pocket as well as chamfer the case mouth inside and out on my RCBS motorized Case Prep Station. I then removed the sizing die from the first station of the Dillon press and reload the lot of preped cases progressively.