Using a primer

It might also help if you use something like Mr. Surfacer 1000 or 1200 as a primer that will leave a smoother surface to begin with because it has finer granules and shouldn't require as much sanding to produce a nice smooth finish, which in turn makes achieving a smooth final paint job an easier task. I generally prefer the jar version over the rattle cans since it can be thinned and sprayed with an airbrush, which allows for greater control than an aerosol can.

You'll probably want 800 or higher. Keep the paper wet and lightly sand until you have a consistent texture all over. The water keeps the paper from loading up with debris, rinse both the model and the paper occasionally.

Okay so, I have my first coat of primer on the model body! Now as far as the sanding goes, how do I do that? :P I mean do I just take some 600 grit sand paper and start sanding it down? How do I know when to stop sanding or when I have achieved whats desired? Thank you in advance, once again!

Until the paint is cured.

What you really need to do is start watching television! Programs like those featured on Spike TV's Powerblock where they regularly show how to do body and paint work...including wet sanding between coats! A good program:

http://www.spike.com/full-episode/super-dually-part-5/41283

You paint a model in the same fashion one paints the real deal!

Nothing says you have to apply a primer. A primer serves two purposes. First to help you spot any flaws in the surface of the object being painted. Secondly to give a consistent base and suitable surface for the paint to adhere.

If you use your method and not getting the greatest results, then you probably want to again wet sand with very fine polishing grit cloths. This will even out the paint surface and give it a better appearance. Even high end new production cars get this treatment as well as a rub out and buffing before being turned over to the dealer/owner...again TV explains such events, just love those ultimate factory programs where they build cars.

When im spraying the primer, how long do I need to wait between coats?

Joshuadude

Generally what grit sand paper should be used for this? And when I sand the primer, how long does it need to dry, and to what degree do I need to sand it?

Thanks for helping me out buddy!

I use 600 grit for sanding out primer and intermediate coats of color.  While for years I used regular wet-or-dry paper, 3M has a new sanding sponge that is great for sanding primer. I think it is 400 grit.  It is a checkerboard-like piece of sponge with holes alternating with the sanding surface, so it really cleans out well.

Many primers are quite thick and leave a lot of residue on the sandpaper.  This is why wet sanding is necessary, or else your sandpaper will clog up very rapidly.  The  holes help it clean up when you dip it in water.  Many hardware stores carry these sanding sponge sheets.  But, paper is fine- just make sure you get most of the sanding dust off when you dip it in the water.

I dry the surface with Kleenex tissues after sanding, so it dries quickly unless the humidity is very high (raining out).  But then, you shouldn't be painting when the humidity is that high (near 100%) anyway.

In reasonable humidity it shouldn't take more than ten or fifteen minutes to dry if you wipe it with a cloth or kleenex.

Generally what grit sand paper should be used for this? And when I sand the primer, how long does it need to dry, and to what degree do I need to sand it?

Thanks for helping me out buddy!

My girlfriend got me this really nice Tamiya Nissan GTR model and im trying to make it look like its worth the 60 dollars it cost haha

welcome to FSM, dude 

wet sanding is simple. On the sand paper package or the back of the sheets it will read "wet or dry" sanding 

this means you can dip the paper into water then sand the model. Generally, this will produce a smoother surface 

dusting the model should be the first or second light coats only. Follow this with sanding, if required. Then a solid spray coat. Follow the directions on the product can