Brother with the recommendation of Motorsil-D is speaking the gospel, but it's a chore to source stateside. It's really not worth the hassle considering that a tube of the stuff will cost about $10-20. ILYY uses it as their response goop of choice.
He thought, until a couple of years ago I bought in at the Spanish Store paying € 5.9 to the tube! then they increased the price even there ...
I think I've tried at least 20 different types of silicones in the course of my experience and I consider Motorsil-D the best for the following advantages:
- It is a self-leveling silicone, then tends to expel any air bubbles created
- Dries extremely quickly, after only 20 minutes you can remove the excess and after 40-60 minutes the yoyo is again playable
- Gives the yoyo a sweet and smooth response
- Very slowly consumes allowing duration (with average playing time) a few months.
p.s. the Motorsil Black, it is a whole other thing ... totally different, with long drying times, too soft and easily consumable... I don't recommend it