So what have I learned ?? Keep in mind I am new to this welding stuff.
Make sure when you are welding that the patch stays flush with the original panel, check it often
Weld some grind some. If you do all the welding then grind you WILL lose your mind
Just grind off the heads of the weld, try not to hit the sheet metal, it will get so thin you will cut the patch off and start over, Please don't ask how I know this !!
I use a 4.5" grinder with a 1/16" cutting disk turned 90 degrees from the weld. Then I just nibble at the weld until flush, then I hit it with a flap wheel and start again
The more you try to get it perfect the worse it gets, A thin coat of filler, block sanded works wonders
Use copper behind wider gaps it works wonders
Heat from grinding also warps, keep a hammer handy to flatten and used compressed air to cool often
Grinding makes your shop dirty
DON'T FORGET TO TURN YOUR GAS OFF WHEN DONE