I have a set of '87 "T" wheels at the shop right now getting refinished. I'm having them done as reproduction '85 GN wheels with black in between the spokes.
The reconditioning process involves:
1. dip the wheels in chemical cleaner
2. remachine the machined surfaces on the face of the wheel to expose fresh metal
3. repaint the area between the spokes
4. clear-coat the entire face of the wheels.
I may have the steps out of order, but the key is remachining the surfaces that were originaly machined. I don't think any form of sand or bead blasting will give you the same look as the original machined surfaces. although it will probably work fine if you just want to clean them up.
As a side note, I wish I hadn't gone this route now as I discovered this afternoon there aren't many tire options for 15" rims anymore.
Especially if you're looking for V or Z rated. A few years ago you could get BFGoodrich Comp TA ZR's (and VR's!) in a 235/60/15 which was perfect for a stock rim - same overall height as the OEM 215/65/15, but wider and still fit nicely on a 7 inch rim.