It doesn't matter if the lube grooves are coated or not, it's the bearing surface that counts. The only purpose of the lube grooves on coated bullets, is to give the displaced bullet metal a place to go.
I am also a convert to powder coating bullets. I do it only on the pistols I use for action shooting, to eliminate the lube smoke.
The instructions I was given, that rolling in a plastic tub for 20 seconds was adequate. It's the spinning that generates the static electricity. Also to add some airsoft BB's to the container to help with the process, maybe 2-3 layers. You don't need that much powder paint to get the job done. A pound of powder should do 5,000 or more bullets. You can use too little or too much. Pick the bullets out with needle nose pliers or tweezers, and place base down on a pan with non-stick tin foil. Some claim they can use nitrile gloves without disturbing the paint. Preheat oven to 400 degrees, and place tray in oven for 15-20 minutes, let cool and you are done. Some do what is called the smash test afterwards. They place a sacrificial bullet on a vice and smash it with a hammer. If the coating stays on, it's good. If it flakes off it isn't. I can even size the bullet down a good bit afterwards, and the paint stays on, it just looks burnished. I have had very good success following these directions from the vendor I bought the supplies from. I have a whole $25 invested in the powder coat project. I bought all my supplies from a guy named Smoke4320 on the Castboolits forum. He has a paint ball supply business. He has his own special powder paints, that seem to work pretty good.
