I've made blendshapes for them , I suppose you could open blender and make even more + or - sizes though!
I do know that if you have everything playing at once on this dick you can run into VRC culling / stopping sounds from playing but that usually wouldnt be the case unless you had throbbing on top of sloshing on top of both particle effects running usually, also certain worlds can kill sounds too like IDLE cube and Popcorn palace.
Well for throbbing to emit sound there are conditions one of which is you need to be >60% aroused , so make sure you have arousal Framework installed and then try ^>^ if you still have problems I'll hand you my discord and we can sit down and figure things out! I know the new SDK has been giving folks issues.