What do you guys clean plastic baths with to degrease the joint before using silicone? Is 99% alcohol ok? 
 

thanks 

I used that IPA and it works well.

IPA is the safe pick on plastic baths, it cuts grease and flashes off without attacking the acrylic. I would avoid acetone or anything stronger, it can craze the surface. One extra that saves callbacks is filling the bath with water before you lay the bead, that way the silicone flexes with the bath rather than against it.

I would just use a decent water based surface cleaner.

The one I use, and I have to clean a lot of grease and oils, contains Ethanol Amine, Cocoalkyl methyl, Ammonium Chloride.

Made by Elbow Grease and called Heavy Duty Degreaser.

Costs about £3.

You really will not be disappointed.