yeah clyon is right, there are many different blasting grits you can get, some you can re-use and some you can't.

Garnet can be re used a couple of times before it looses its 'edge', when its fresh it leaves a rough finish, but primer and paint fills it well. We mainly use it for stainless steel jobs, but can be used on anything.

Black slag(blast furnace slag) is really rough and can only be used once not as good of a finish but is very cheap.

Stauralite(combination of the two above) is another product that we use at work most of the time for mild steel applications.

depends on the size of the blast hopper as well, we use a portable blast hopper, informally known as the 'mighty mite' doesn't blast anywhere as good as the 'big hopper in the workshop, the 'big boy' uses a 2inch bull hose, so you have to hang on!!!

Its all good! thats sound right, it should come up good.