Not a painter but I hung around some.
I would:
-DA the existing surface only down to the base coat.
Campbell Hausfeld Dual Action Sander - Walmart.com.
-Hand sand the edges carefully.
-Mask
-Use self-etching primer.
-Mist it with black paint (reveals low spots) and go over panels with a long board.
-Repeat.
-Base/Clear.
Or sand to base and use a single stage with binder, if all it needs is freshening up.