I'm going to use Collinite 915 before the winter. After washing my car can I leave it wet or best to dry?

 

Collinite recommends using a damp cloth to wax.

Defo dry for me. Even wet drips seem to cause havoc for me.

Usually use a foam pad to apply, wet but wrung out really well.

Using a damp cloth to apply the wax is rather different than waxing a wet car. You'll just end up with the applicator wringing wet and the wax will probably emulsify then.

 

Definitely dry before you wax would be my suggestion.

As above...always have a damp applicator pad and apply sparingly to a DRY car

Buff off after a few minutes..so half the car at a time, then buff off