It's easier to weld with a flange on the new metal. The tool is called a flanger. If you just butt up the new piece. It's so easy to burn through the steel. Not trying to tell you how to weld.

You probably already know. If you do just butt the metal, take a piece of copper and put it on the back of the area your welding. Then you won't burn through and will get a nice weld. Just a small piece of copper will work. You can keep using the same piece.
Just trying to help
If you do get a media blaster. A small one will do. You will need a good compressor. I wore out a 33 gal one. Just get the medium grit. It will eventually turn to fine. Use a pool skimmer screen to filter the media and reuse it. You should only need about five bags to do the whole car.
Here's what mine looked like.
