When i was on a UPP kick, i only used it.
When i was trying DP's sealant, i only used that.
I topped EX, but never did with NXT.
I really didnt like to top my sealants because i liked to add another layer when i wanted to.
I switched to Zaino, so Z8 is perfect for this.
But if i were to use the JW line of products, his nuba QD would make a nice addition to his nuba topper.
Basicly what i am getting at, with the evolution of spray boosters that actually perform, i would have no problem topping a sealant now.
Although, i have a hard time seeing the difference between whats on a very well prepped paint.