Do I have the right steps?

Farmall Super C

For sheet metal

1 Sand the paint off to bare tin.
2 Use body filler to fill in small dents and craters
3 Use 1 coat case ih buff primer with hardener.
4 Then use Case IH primer with hardener (2-3 coats and sand between coats)
5 Lastly apply Case ih 2150 paint with hardener (2-3 coats) (Do I have to sand between coats for this one?)

Then for the Cast parts

1 Wire wheel the cast parts to bare iron
2 Use 1 coat case ih buff primer with hardener.
3 Then use Case IH primer with hardener (2-3 coats)
4 Lastly apply Case ih 2150 paint with hardener (2-3 coats)

Is there any thing missing that I should do or anything I should change?

Only an opinion not etched in stone:
Sheet metal #3&4: I didn't know you used hardener with CaseIH primer, is that on the can of their primer? If not you might end up with a mess. Best to use 2 coats of epoxy for #3, and use sandable urethane surfacer in #4. 3 coats of surfacer and sand, repeat until smooth. do not get it too thick, in other words you will sand most of it off. Remember that you need supplied air for the isocyanates in the hardener. If you don't want the iso's, there are other primers and surfacers that can be used that do the same thing, but they can sink into the sanding scratches. Or just use the CaseIH stuff without hardener.
#5. You don't sand between coats unless you have a rough finish (poor technique) or runs in the paint.
Do the cast the same except that you don't use surfacer.
PPG numbers are Omni MP 170 epoxy primer, that uses a non-iso catalyst, and PPG MP 182 urethane surfacer over the epoxy on the sheet metal. For a non-iso surfacer use Omni MP 181. These should be safe to use under CaseIH 2150, I will not promise, but would not hesitate to use it myself if I ever get too poor to use acrylic urethane. Cost will be maybe $150 more than the IH products.