I haven't had real good luck with the "solder-it" either, I've tried the lead free and the pot metal solder both.
I've just used the regular old garden variety lead based stuff and it plates fine, properly cleaned.
On sand blasting,
DO IT! In fact, take a look at a post by 48 Buick (25 NOV '04) which describes the most fool proof method to a "t".
Good luck!
