trouble using bondo

1st you have to make sure your patch work is butt welded the better your metal work is the less bondo you need. There is epoxies on the market that you can apply you filler on top of this way you get a premium chemical bond and have no rust issues down the road,you ever grind old bondo out to find rust under it ? that's caused by the chemical reaction from curing.If you use a premium filler like evercoat,gold or xtreme,there's little to no pin holes. I don't use body butter for my final coat i use polyester putty ( 2 stage putty)
Like i said i'm just east of ya Pm me if you need any more help.