You can do a burn on it for peace of mind but I think if it was me, and I was down to bare metal, that I would build it and season it.
There is debate on this and I don't intend to start a pissin match but every comp I go to, there is at least one team cooking in a galv trashcan.
I cant see how your drum could have anything bad left after the blast.
The lid can be a touchy area, some fit good and some not so good.
On one of my drums, I cut a large radius on a 2x4 and put it in the vise.
Then I used it along with a rubber mallet to form the lip of the lid flat.
Then set it on the drum and again used the mallet to tap down four places of the lip to form to the barrel.
Gotta be careful doing this cause the lid will try and shift sideways and get all goofy outa wack.
This one, the lid works OK but not great.
On my second drum, I set the webber lid on top of the standard flat drum lid.
Welded the two together on a very low setting. Mainly to seal it up more then make a full pen weld.
After it was welded I took a die grinder and cut the center of the flat lid out and ground it smooth.
This one works Fantastic!!!!!!! Its a very nice tight fit.
If it does not make sence shoot me a PM and I will post ya a pic.
Not sure if I will be on tomorrow since I am attending the Lenexa BBQ contest. But I will try and atleast check in.
Tom