whizzerick,
Being a foundry type, you are familiar with sand. It's sort of nasty stuff and not the thing you want in your new engine. If it were me, I would NOT bead blast or sand blast any piston.
Clean them with solvent and a soft wire brush. If there is tons of carbon on top, you can scrape it off with a putty knife, or do the oven cleaner routine.
The ring grooves have to be clean and carbon free. If the pistons have any drain holes in the oil ring groove they must be clean too.
Stuart
