It's pretty obvious what its coming to. Either do a really bad job and keep your 'costs' low. Or build a frame. Surely you have a mate who can weld? Or has a welder??

A frame shouldn't cost you more than two cheap or second hand engine stands and a 6.5meter length of square hollow. You could model the thing and build it out of off cuts from a fabricators off cut bin. $2 a kilo of steel is about the going rate for offcuts, probably a lot less in the land of plenty.

Otherwise, take the doors and guards off and tip the shell on its side onto a mattress, lean it against a wall. Hook into it with a grinder and use a roller to apply a generous coat. That's about as cheap as you can get. Doesn't look good but it won't damage the shell and you can get good access to do the job properly.