How about an alternative method with less work???
If this was my project this is how I'd do it........\I'd not strip the entire paint job. It looks like it is in great condition and much like a real automotive body shop....if it's stable paint over it.
It does need some prep. With a very fine grit sanding stick I'd sand over the lettering and any numbers and data. A light sanding overall. I then wash the body and allow to dry.
I then apply a primer sealer. My favorite is automotive brand Dupli-color gray primer sealer. (sold in big box and auto stores) Two very light coats and you should have a nice even gray surface and if applied right smooth and ready for paint. It needs a few days maybe a week to dry. (I place mine in a dehydrator to spped this process)
For the easiest color coat I use Tamiya brand spray cans. (hobby shop) It is a super thin lacquer with great coverage. Two to three coats and she should be ready to decal. Now if you have extra detail parts they need to be applied before primer.....then just as above. After decals you can apply a dull coat from Tamiya or Testors if you want a flat finish......or gloss if you want 'shop new' paint.
I know my way is very different than most. But I'd put mine up against many of the works of other (they do great work too) and it is and easy process that yields results that are hard to tell from a complete strip and paint. Thanks!
My way......
This MTH caboose was a McDonalds set version. It was yellow and red with a big french fries package and McD logo. It was all lightly sanded and primed over.
