When removing the firewall brackets, there were some tears and holes from the removal process:

I wanted to take advantage of having the hole for accessing to smooth things out.  There was a tear right where I need to cut which I wanted to repair:

So – I went to Harbor Freight to buy a hammer and dolly kit to use rather than ordering one from the internet and waiting.  I still might do so to get a higher quality one later, but this met my needs for now:

After using the hammer and dolly to get it somewhat flat again:

Then I ground around what I will be welding with a wire wheel brush:

Used some Eastwood Metal Wash to clean the area and sprayed with some U-Pol weld-thru primer.  It was roughly 30 degrees outside, so I kept the garage thermostat set to 70 all morning, then turned off the heater and sprayed two coats 20-30 minutes apart.  I used a fan to help air out the fumes and after an hour or so, turned the heater back on and all was well!

I also changed the wire in my welder from .030 (from the jig) to .023 for the car sheet metal.  I will brush-up on some spare metal and then weld-up the holes.  Then I should be able to do a final cut and weld in the toe-board patch!  Might be able to get some more done throughout this next week starting on Wednesday.