ALWAYS clear between layers, but innercoat is only required if you are going to try to dip to that layer past your normal clear recoatability window. If you can get to it before that 8-12 hour window, you can just use normal clear.
Go figure. that patent runs out on the old system that worked well for years... and suddenly they will set you up with some new parts for this great new system they developed. Oh yeah, and BE CAREFUL... there are unscrupulous companies out there that want to sell you that old terrible system at a greatly discounted price compared to what they sold it for. Good thing you guys are too smart for that and will only trust 3M representatives to treat you right!