You still have some work feathering the filler. After you strip, work on filling and sanding. Airbrush (or rattlecan - I always prefer airbrush) Mr. Surfacer 1000 as a primer. Then wet sand if necessary. Super fine grit with a backing. 1200 grit sandpaper wrapped around a 6" steel rule as an example. Depending on how much leveling your topcoat gives, you may have to "rinse and repeat" working up to 4000 grit sandpaper. On some models, I've "sanded" using Post-it note paper pads (dry).
Are you sure you don't need that escape hatch?
"Sixth is the roof escape hatch that is in place on all Funny Cars since the founding of the division in the early 1970s. This device allows Funny Car drivers a safe means of exit during an engine fire rather than falling out of the car between the frame and fiberglass body, and possibly running the risk of being run over by the rear tires." - Wikipedia