Since I built my track, I have been using sponge tires on all of my cars. To get enough bite, I had to use a home brew traction compound made from oil of wintergreen and STP oil treatment. I applied the compound to the tires, not the track, and I wiped it off the tires before the car went back on the track. This did a good job but only lasted for a few laps. It also was messy and left more residue on the track than I would like. But it had the smell of the '60s!

After reading a lot about silicone-coated tires, I decided to give it a try. Man am I glad I did! I won't go back to plain sponge tires on my track again. These things are easy to make and they get consistent bite lap after lap, provided the track is free of dust. By cleaning all the traction compound off the track, the stock rubber tires on RTR cars work much better as well. This is how I make my silicone-coated sponges. With a little practice, you can make a set of tires in about 10 minutes.

I start by chucking an axle in a cordless drill and mounting a wheel/ tire on it. I clean the tire very well with lighter fluid. I use plain Permatex 16B black silicone. Others may work just as well.

I first put globs of silicone all around the tire as I turn it slowly with the drill. Using my finger, I work the silicone into the tire and around onto the sidewalls while spinning the tire slowly.
At this point I wipe all the silicone off my finger. I have found that the next steps work better if there is no silicone on my finger. Using plenty of saliva (I have tried other things but spit works the best) I spin the tire slowly while evening out the silicone with my finger. I wrap the silicone around the edges to make it as slick as possible all over the tire. Once it is evenly distributed, I put saliva on a piece of glass and spin the tire very slowly against the glass in the saliva to get a very smooth, flat surface.
Spinning the tire on the glass will push some of the silicone back out to the edges, so using saliva on my finger I smooth the silicone out with a very light touch. Once I get it smooth, I take the axle out of the drill and stick it in a piece of foam to cure. They will cure faster if I put the tires under the lamp on my workbench.
This process may seem a little tricky at first, but with a little practice you will quickly get the hang of it. I have found that you just have to perfect your own technique. Once you do, you will be glad you did. I have even taken old sets of dried up orange sponge tires and coated them. When finished, you could not tell they were ever orange and they had plenty of grip! The silicone tires work best if you lower the rear of the car down gently on sandpaper to scuff/true the tires.