I want to weld shut some holes in my engine bay and I figured I can rent out a MIG welding machine from Home Depot. Thing is, I dont know exactly what needs to be done to fill in the holes. Can anyone explain the process to me step by step? I searched and came upon nothing. There are write-ups but people show the outcome of the work, not the steps leading up to the outcome. I also drill out the tac welds from my passenger side mount since I'm going K, but now I have alot of holes where the mount use to be. How can I close up those holes?

 

Back them with copper when you weld them up.