Do you know what RG's are made from? Something tells me it would be mahogany, but it could be anything I suppose. You could use pretty much anything(wood wise) to fill the holes, within reason: maple, poplar, alder, ash, mahogany, etc... Just remember that some woods need to have their grain filled before any type of finish is applied.
For the finish:
-if there's any porus wood, fill the pores. you can get that from stewmac and maybe a hardware store. I always order it from stewmac so I've never bothered to look anywhere else.
-I don't imagine you have a compressor or paint gun so I would go with aeresol cans if I were you.
-First prime the body. If you have an automotive store like autozone or pep boys around, buy your primer, paint, and clear coat from them. Auto grade paints will stand up to the abuse a guitar gets better than furniture grade stuff.
-Once you prime it, sand down any imperfections with wet sandpaper to about 800-1200 grit.
-Put down your color coat. If there are any imperfections you'll have to sand it down and respray the color coat. You can't clear over a color coat that's been sanded smooth, you'll see the scratches. Make sure to have a few coats of the color on the body.
-Put about 5 coats of clear on the body once the color coat has dried for a few hours. Wait for the last coat your sprayed to tack up before spraying on another coat. Let this dry for about a week.
-Wet sand the clear coat to about 2k-3k grit with wet sandpaper. Then buff your heart out with a coarse buffing compound, then a medium buffing compound, and finally a fine buffing compound. If you want it to really shine, then wax the whole thing with turtle wax when you're done.
There are definitely easier ways to do this. You could use laquer for instance, but using car quality products will give you the best results when it comes to opaque colors or just clear coats in general.