Dupont used to sell a Blender that you could mix in with the material in the cup (19301S). I don't see it on their website anymore but still do at my Jobbers. I have it and have used it several times. They do still list the same thing in a rattle can (A-19301S) and I hear tell it works just as well.
I generally clean and scuff the entire panel (scuffing gel/paste with a gray scuffing pad) first. Then effect the repair as required (depends if it needs leveling or not) then lay a couple of coats of base (stepping out the second past the first, then the third past the second if needed).
If you get the Blending Agent that can be mixed with the Clear in the gun, go ahead and lay the first coat of Clear out past the last coat of the base, then step out the second coat of clear past the first (like before).
You then added the required amount of blending agent to the cup with the remaining clear in it and step out the edge of the last coat of Fresh Clear. Dump what's left in the cup then use the Blending Agent straight and step out past the final edges. Ideally yes you should clean the gun before this step but I use the PPS System so I just grab another cup, I'm not to concerned with what's left in the passages of the gun.
I don't mask the panel when I'm blending the Clear Coat either.
Blending is a art and takes some practice so don't be disappointed if you don't get it right the first time.
Thoughts and comments expressed by me are mine based on my own experience and research and shared here freely. I am not a professional nor make any claim to be as such