cheap, fast, easy, auction?
hvlp or syphon gun from (walmart, tractor supply or harbor freight ). can get one in the 20-35$ range to fit that bill.. usually a 1qt cup. gravity or bottom hanger.
use an inline air filter water seperator.. you can get disposable ones for about 6$$ and you toss them each day.. they fo inline ..
you will need a pressure regulator to match the guns needs .. on the cheap.. you can get orificed units with a small gauge or 2 in/out and a knob. .. not great.. but works.
alkyd enamil paint is as chap as it gets. it's also inexpensive too. mineral spirits for brushing and usually naptha for spraying.. but read the paint you get.. there are some different formulations that like other reducers.
hardner is it's own can of worms. It's one of those things where if you are not sensitive to it. you don't notice it. if you are sensitive to it. as little as a whif can put you out of commission.. supplied air kit will eat up your entire budget.
some people buy a good disposable carbon filter with 'rescue' hazmat filter and just limit exposure by painting open air, preferably in a breeze.
i'm not giving you any sugestions there other than to read lables,,, be informed before you make your choices..
lack of hardner in alkyd enamil paints means it takes longer to cure and may have less luster and scratch resistance. Given that this is an auction paint job.. .. um.. i doubt it matters. I'm not a fan of auction paint anyway.. so...
be safe.. good luck.
ps. I've painted a ton of tractors with alkyd and syn alkyd enamils. with some practice and care you can make great loking tractors for dollars, not hundreds of dollars.
Now if you want to get into auto quality finishes. research urethanes and such.
right now you are probably looking for a single stage alkyd or syn alkyd paint. magic has them. valspar, if you can find it has them. nason has them.. I currently use nason syn enamils since I can't get valspar anymore... i have tried majic.. it's probably the cheapest on the market...
do some reading on prep.
you will want to degrease and use a solvent or wax remover.. oils and water will cause visible and distracting blemishes and artifacts in the paint.
some guys degrease, pressure wash, then use a soap like purple stuff and another pressure wash, dry, sand and then primer and paint and then load and sell..