If you're talking about their polishes (Z2,Z5) I would suggest you apply by hand. Sal suggests using a 100% cotton pad, but I like using one of those 2-in-1 pads (one side for cleaner waxes/polishes and the other side for LSP's). I used to apply Zaino by PC using a LC red pad, but it was absorbing too much product.
I only use the cotton pad. I use 1 side for one coat and the other side for 1 coat. That way I can get 2 coats of Zaino on the car using 1 pad. Helps to keep the cost down some what.
Zaino Fusion or ZPC is the only true abrasive polish that Sal offers currently. AIO has a small bit, but not a true polish. Everything else labeled polish is actually a paint sealant and best added/removed by hand. Remember to use as little as possible ...
For Zaino Z-2 or Zaino Z-5, I would use a blue pad. Z-2 and Z-5 are best applied by hand because typically using a Porter Cable and a pad ends up using too much product.