Seeking order of operations and other opinions

I’m planning to modify some side mount pickup toolboxes as I mentioned in this thread:

They need quite a bit of rehab. After I mod them and clean them up I’d like to powdercoat them.

I score the hinges as beyond saving. I plan to cut them out and replace them. I’ll probably look for some stainless hinges. I’m pretty sure I’ll end up powdercoating the cover and bottom separately. I don’t see a good welding option so I’m thinking rivets or carriage bolts. Those will be easier to get around than a weld, but nothing will be perfectly secure. It would not take much more than a can opener to get into these anyway. I intend to improve the locks, but we’re not going to look like a safe here.

I know I’m going to need to clean up the rust before welding, at least around the welds.

My real question is how and when in the order of things should I attack the remaining rust before powder coating. It’s too big to soak in something or fit in either the sandblast cabinet or vapor hone. I’m thinking wire brush for the bulk of the surfaces, but getting into inside corners with a wire brush is probably not going to work well.

I’m wondering if this would be good enough as a limited use-throwaway sandblaster:

https://www.harborfreight.com/21-oz-hopper-gravity-feed-spot-blaster-gun-95793.html

I know it’s junk, (calling it a toy would be insulting toys) but is it an alternative, or what are my options?