I also use wax on my paddle. The trick is to use a wax that:
- supports high temperatures (the inside of the hand): base or tropical grade. It thus also does not melt in the car
- lasts long in use
- does not create big bumps (you may get blisters)
- does not stick too much (you will get blisters), avoid the ultra sticky ones like the Fu Wax
By looking at the reviews(*), I chose an Australian one: Mrs Palmers Tropical, it works quite well. It is consistently reviewed as the longer-lasting one, and very adapted to hot waters. I didn't try their new "Bali" one, though.
I think it belongs to the same group as Billabong, so you should find it in any store carrying Billabong gear.
As a backup, any "base" wax should work too, but avoid the ones designed to create bumps.
(*) E.g:
www.globosurfer.com/best-surf-wax/worldsurfers.com/best-surf-wax/www.surfnation.com.au/blogs/news/ultimate-guide-to-surf-waxstabmag.com/hardware/stabs-best-surf-wax-test-guide/surfhungry.com/best-surf-wax/