First... you DON'T have to prep the furniture before using Rub n' Buff (at least I never have), other than making sure it is clean of course. No sanding, or stripping or anything like that, (this is assuming that you don't have any chips, scratches, cracks, holes, or any other damage that needs fixing. Rub n' Buff WILL NOT hide damaged areas. It will highlight it, if anything.) I haven't had any problems applying it over painted furniture, stained furniture, and unfinished furniture.
Second... Fill a spray bottle with Deglosser. You can pick up the Deglosser at Lowe's.
Third... Spray the area you want to work on. By area I mean the entire side, or top, or draw fronts. Mist the whole area, but don't spray so much that it drips. Here is the side of the desk with three sprays of Deglosser you can spray until most of the area has been covered. DON'T SPRAY SO MUCH THAT IT RUNS DOWN THE SIDE. The Deglosser evaporates fast so you will want to get straight to applying the Rub n' Buff.
Fourth.... Apply a rather large blob of Rub n' Buff to a cloth. The bigger the area the bigger the blob. Here is a picture of the size blob I used to cover the side of this desk which was 16" x 27". I had already used some of the Rub n' Buff on another project so even though it may look like I use half the tube... I didn't. Just squeeze till you have a blob about the size of two FAT peas. I will say that having a little larger blob than you need to cover the whole side is better than having a blob that is too small. Too small of a blob will create an uneven look and you'll have to do it over. As soon as you do one side you will get the feel for how big of a blob you will need to continue on the other areas (I hope). You can smear the Rub n' Buff around on the area before you start rubbing. Smear some from your cloth on the top, bottom, sides, and in the middle then start rubbing the smears together.
Fifth... Repeat until you've cover the whole piece. Pretty easy really, and doesn't take very long to do.
Sixth... When it's dry, buff it with a clean cloth till it's super shiny!
A lot of people have asked if Rub n' Buff needs to be sealed. This is not such an easy question for me to answer. Rub n' Buff is a metallic wax and I believe is NOT intended to be sealed. Some people say that if you spray it with Polyurethane it will mess up the finish. Here is what I have found... It depends on the color you are using and what you are using it on. Some colors, like Pearl Blue for example, I have used on full furniture pieces (wood and vinyl), and have had no problems with it rubbing off and have had no problems cleaning them with pledge furniture polish or even a multipurpose cleaner. Other colors like Silver Leaf for example tends to give off a residue (rub your hand over it and there will be a hint of silver on your hand) no matter how much you buff it. I had this happen with the desk I posted above. I DID spray a light coat of Polyurethane over the desk and it didn't mess up my finish but, I was VERY CAREFUL NOT TO OVER SPRAY it. No bubbles or drips! That took care of the silver residue.
***UPDATE, UPDATE*** Spoke with the good people at Rub n' Buff and they advised that Rub n' Buff can oxidize and change color a bit when used in high humidity climates (like Florida). A sealer should be used, and a water based Varathane sealer was recommended . (However, I use a spray Poly and have had not problems.)