If you can see it there's a chance you'll see it after its coated. The powder does have some fill and flow characteristics but you take your chances that may hide minor imperfections. Use your judgment and ask your coater. If the rims are clean (no damage, no rust, no peeling etc...) they may not need blasting. You may just need to use a fine emery cloth or even an aggresive scotch brite pad. As for a price guesstimate ....a 1 piece rim... maybe $35-$55 ea. just the ring maybe $25-$45 ea. but there may be a minimum for setup. Ask your friendly neighborhood coater.