I also have been using Zaino for years, especially on Black vehicles,especially Black Vettes/Vipers, and never really had a problem, yes it takes a little longer to set up, but I have found using a micro bonnet over a wool pad makes it easier to remove,After chatting with Sal, Also Note Temperature/Humidity plays a big factor in the set time also.
I actually have been very pleased lately using Meg. Synthetic Sealant 2.0 #21instead of Zaino, and is a dream to apply and wipe off, and the gloss depth/durability/availability over having to order Zaino makes me very satisfied, almost to the point that I would say amazed in how this product is so easy to work with.