Since the trim die is also a sizing die, I wouldn't resize a case that has been sized and trimmed, just to clean a flash hole. You may also find it difficult to just trim without sizing with the RT 1200 die.
Here is one of several ways I do it. Size and trim with the RT 1200 on the XL 650, and use a Lyman M-die to expand the neck. When the press is set up to load, use either a Lee or Dillon depriming die in station one to either deprime, or punch out media, or just center the case in the shell holder.
My preferred procedure is to tumble/clean, and lube cases. Then on the XL650 I deprime at station 1 with a Lee depriming die, at station 3 I size and trim with the RT 1200. Next I wash the brass with Simple Green and water, rinse, and bake in the oven at 250 for 30-40 minutes. When I load the cases I use a Lyman M-die at station 1 to expand the necks just enough to start the bullit, load as usual.