A pourable silicone works well for coating an existing rubber or foam tire, I am not sure that it is the way to go for moulded tires. A pourable silicone is a silicone elastomer dissolved in a solvent, a ketone like MEK or MIBK works best with silicones. When I was working with silicones I would react a silicone polymer with a silicone type crosslinker using a catalyst to make an elastomer. You could fiddle around with different combinations for a long time without getting a decent tire. The other problem is the mold, 1/32nd cars use goofy rims with a center rib. Making the mould for that type of wheel is more trouble. Since silicone is difficult to sand you would want the tires to come out as true as possible.
HO racers use a lot of silicone on sponge tires, they give terrific grip and are more forgiving on a bumpy surface. They are not often used in 1/32nd scale, I presume because they do not look like 1:1 tires.