Wow! Good eye, I had to go back up and see what brush you were talking about!
That is a cheapy steel wire brush I started to use and realized it wasn't going to do a thing against the build up that was in there.
Thanks for the tip on the steel wire attachment for a grinder, I'll pick one up today.
I also bought some rust converter, but I'll definitely be taking all the rust off first and spraying that on as an extra precaution before I apply the high heat paint.
So has anyone else taken one of these with the bolted on firebox and had it welded on? Can I just have a welder run a bead around where the firebox attaches to the grill?