Between life and work, the longest time period the bondo would go Unpainted would be about 2-3 weeks.Click to see full answer. Subsequently, one may also ask, how long before you can paint over Bondo?Bondo mixed to the color swatch will begin to cure in less than 10 minutes at room temperature.Additionally, is Bondo body filler waterproof? Fiberglass. Choose between Bondo Fiberglass Resins, Bondo Fiberglass Repair Kits or Bondo Body Fillers. Bondo Fiberglass Resins and Repair Kits are 100 percent waterproof. Beside this, how long can body filler last? You only want to mix what you can use in about 10 minutes. Properly mixed, body filler will begin to thicken in 10-15 minutes, and be fully cured in 30.Does Bondo need to be painted?Do not slap Bondo onto a smooth painted surface, it is not going to stick very well. The paint should be sanded off, to the bare metal, and then apply the filler. A 36-grit to 180-grit surface is ideal for body filler application.