Need cast 30/30 info bullet prep.

I have PC'd before checking, but it's easy to overcoat the GC shank so they don't fit. I would suggest at most 1 coat of PC, check and size, then the 2nd PC, and optionally size again.

If you PC you won't need gas checks. I have checked some PCed bullets and used them in my Mosin Nagant and a few in my Garand and did force some gas checks on, but I didn't really need both the PC and gas check...
http://castboolits.gunloads.com/forumdisplay.php?184-Coatings-and-Alternatives

I size, powder coat, then size again/out check on.

Tho you don't need to check when powder coating, for hot loads i would. I will help with gas cutting.

I PC my bullet, quench after curing and apply gas checks and size to the desired diameter I need usually while the next batch is curing, I have no issues putting the checks on after coating. Those bullet then sit for about a month before loading to age harden, I have enough in the pipeline that the wait time isn't an issue.

People tend to use to much powder and over coat there bullets which can make it hard to install gas checks easily. If your bullets are properly coated you should still be able to see all the fine line details of your bullets a good powder goes a long way.

Here are some NOE 124 gr. TC .358 bullets I shoot in 9mm and 38 Special coated with Smokes Super Durable Clear, Gator checks will basically fall off the gas check shank even after the bullet is coated if you don't hold them on while placing them on the sizing stem.