I use Sandblaster sand paper from any of the big box stores.  The best I've found for longevity.  I sand dry and flick the paper with my finger to keep the grit clean.  I use 220 with light pressure to begin.  I then use 320 for the majority of the sanding and finish with 400.  If you go finer than 400, you may get the surface to slick for the paint to adhere.  Not to be a smart mouth, but there is a lot of info here about Rustoleum paint.  A search will answer all of your questions.  I've used Rustoleum paint for my models for 20 years and never had problems.  But, it will not give you a "show quality" finish.  It will give you a nice finish for sport flying.

Paul

    HiPaul:

    I did a search for sanding Rustoleum paint but I seemed to not find what I wanted thus the question on this site.

                                                              Thanks for the reply,

                                                              Frank

RustOleum can give a good finish when applied in light coats, but the secret is to allow it to cure for a couple weeks.
Then it will be pretty much fuel/ castor proof.