how do i shape body filler?
i have a large dent on a rear quarter panel on a 6th gen civic coupe
and it goes from the rear wheel flare to a bit above the the body line (that stretches from the trunk to the headlight)

how do i shape the bondo to the old body lines?
and is there a tip for making it smooth? i've tried it once, and it came out with a lump in the middle that showed once it was painted, but i couldn't see it at all before any paint was on it.

 

Use the longest sanding block you can to get it flat. Remember, your body filler shouldnt be more than the thickness of a dime. When you think youre close, use a guide coat and go back over with a sanding block. Then youll see high and low spots. But honestly from the way you described this dent and without seeing pics, it sounds like it may be too big / deep for body filler.

 

I concur. Pics would help but sounds like a good candidate for a stud gun and slide hammer.