Should you blast inside the Vee ?
Would that make the belt surface a bit too rough ?
How about painting inside the Vee ?

If just needing paint removal, I soak them in lye. Lye doesn't attack iron or steel, but it turns paint into goo that falls off or washes off. Leave the pulley in the lye for several hours, depending on how strong of a solution you have.

I blast and paint them, Never had a issue.

blast and paint.
IF blasting roughs up the inner surface the belt will smooth everything out asap when running. and in my OPINION, the rough part won't wear out the belt.

Same here.No problems.

I wouldn't use something that roughens the metal surface. Use glass. If the pully Vee is badly rusted, might want to pick a different pulley. I bead blast them and wire brush the Vee (with bench grinder). Paint. Paint in V will rub off with belt.

I sandblast/glassbead pulleys completely, have been for decades, paint the entire thing, the belt will remove the paint with no ill effects to either, powdercoating is the only process that causes issues...

OK , Thanks gents, one less thing to wonder about.

If you have anyone in your area that does vapor blasting that would leave the best finish on your pulley drive surface. I recently purchased a vapor blast cabinet for my motorcycle shop and it is awesome.With the media suspended in water it blasts indirectly,the finish left behind is smooth and shiny VS the dry/dull finish of dry blast. Bare steel seems to be resistant to flash rust and it wont remove any stamped in numbers either. I bought it to do mostly aluminum parts and use glass bead mixed with the water.

https://vaporhoningtechnologies.com/

degrease and then EVAPO_RUST< RINSE and paint