I reload for the .280 and have tried many options. The most expensive option is to buy (if you can get them) the new factory brass stock from custom manufacture.
The oldest solution option is the use of belted magnum brass, but I never liked the big "ring" just ahead of the belt. But it works.
I tried the RUM cases, but you have to shave on a lathe about 0.010" on the outside of the case to form it as a .280
Since some time, I use the .375 Ruger case to make my .280 Ross. Can't be better than that.
I use a standard .303 Brit extractor for more reliable extraction of the cases with a smaller rim than the original.
As for powders, IMR / H 4350, IMR / H 4831, RL19, RL17, W760 are powders I tried and they all work well.
Regarding the bullets, some will shoot .284" bullets, but mine doesn't. I use to get Buffalo Arms .287" bullets but they now don't ship this side. An option is to use the Hawk or the Woodleigh bullets.
The 7X61 S&H was greatly inspired by the .280 Ross (and, it's overpressure twin, the .280 Halger) and have a very close case capacity, but works at a higher nominal pressure. You should be able to at least safely meet the starting load of the 7X61 with the .280 Ross.
For the dies, the CH4D usually have them stock.