Im going to stick to baby oil. It is cheap and effective but takes longer to dry. Really added a higher gear to my cheap chinese rubbers, but made the rubber a little springier in the low speed game. Made spinny serves spinnier and made looping underspin much easier. My process if u are interested, otherwise skip to last paragraphs.
1) Apply a thin layer of glue to slow the absorption process. Let dry.
2) spread liberal layer of baby oil with paintbrush. I drop several drops on the sponge and start spreading. Not too much to wear it starts dripping on over the sides, but enough to have a coat. Wait 12 hours.
3) at this point there is a layer of mush on the sponge as the glue and oil has congealed beyond absorbtion. If the rubber had a reverse dome, by this time the rubber will have leveled. Apply second layer liberally like the first and wait another 8 to 12 hours.
4) depending on the rubber there will now be a dome of around 2 cms. If this is a h3 neo, u are done with the layers and start to wait. Apply a third layer if u want more and wait for 3 to 5 days or until the 2+ inch dome diminshes.
5) apply glue to rubber and paddle and stick it on.
This has been my most recent method. The slower the process, the more through the results. Rush it and you can ruin the rubber.
I am sure the more experienced users have better advice then i, as i only recently started messing around.