For primer it would be used when doing large areas in hot weather, very much needed in SE in summer times.
Clear could be used for same reason but I see it more as a finale flow coat.
Something I did the a while back had a panel the after three coat busted out in solvent pop, here and there, my fault for rushing last coat.
Added, some to clear and sprayed a double coat non stop, not a pop left, now that was a flat surface, so a side panel you would need to be more careful.
It was pretty when done, kind of left me speechless to turn a cluster, into a perfect surface.