When to add filler?

[blacktop]

Need help on the best way to go about when to do the filler work. I have the 1/4s stripped I DA them with 80 also the roof once I had them sanded I put ospho on them and was planning on putting the car in DP. Now I'm thinking if I should just to the mud work on the bare metal then Dp. I can't work on it all the time so next is to strip doors and fenders. This is a 46000 mile clean Chevelle. Thanks for any suggestion...