Applying a paste wax with a machine doesn't really do much. You get it on the pad however you need to. Some use the butter knife while others just shake it out of the jar and rub it directly on the pad. Either way works. I don't see much point in it. There are some things in detailing that I just enjoy better doing by hand and using paste waxes is one of them.
Wax is used to give a 'wet' look that sometimes sealants can lack. I have really seen no visual benefit to topping a sealant like Wolfgang or UPP with a wax. The reason I do it is because P21S/S100 has a really cool way of rinsing clean in the rain. When my car is dusty and it rains on it, the dirt seems to rinse off mostly instead of leaving little dirty waterspots. Same thing in the winter. Instead of nasty road spray making my car look worse, the water just beads up and runs off and takes the dirt with it. Its an effect that I have not seen any other sealant or wax accomplish. That is why I top everything with it.