Using lead to fill trim holes

My main concern after attempting for the first time is: Can holes in body be lead-filled without removing all of the panels and laying them flat? I don’t own a welder and found lead to be the most economical alternative, but after countersinking the holes and tinning them, my lead all runs through the hole and out the back. These are the holes for the vinyl top and belt trim I am not reusing. I’m afraid I am going to have to remove the fenders and doors, and I can’t even guess about the quarters. Does this sound right to anyone, and what do I use to back the hole to keep the lead in it? Thanks