I prefer etch priming. I was convinced by a demo piece at the Precision Paints stand - they had brush applied some to a strip of brass and invited all comers to chip it off. You couldn't and in fact it was wearing down to the base metal, rather than chipping.
As Martin says, reds do have a translucent tinge. I would personally use the grey etch primer sprayed, then a light coat of Halford's red oxide primer (but really used as an undercoat) to colour this before going in with the red. I do genuinely think the red undercoat improves the eventual red finish of the model.