I will be the first to admit I do not know how to paint, but I can paint good enough to make a cub cadet look good.
There is a lot of good advice on this thread which will be very helpful. As I am no expert, I just state what works for me.
Painting is a learning process for sure. You can't just take a few notes and become an excellent painter.
Like me, If you do not have a nice paint booth, there are other factors that will affect a paint job. If you are painting outside, you have wind, dust, bugs that love to land on the paint, rain (which will ruin a paint job), etc.
I built a temporary shelter on my trailer to paint in, and works fine. I always spray bug spray around the outside to help keep the bugs out.
The products I use work well for me, and the only issue I ever had was the rusty metal primer made by Rustoleum which does not work at all with Case Irongard.
I have not had any problems with the paint going dull after a year or so, but I keep them inside out of the sun. If I leave a cub outside in the weather, I am not going to paint it anyway.
Here is a pic of my dirty work tractor that I painted 12 years ago. It still has plenty of shine under the scuffs and dirt.
Here is a pic of the 122 I fixed up for my dad about 6 years ago. It has been sitting outside under a shelter since then, until recently.
As you can see, it still has plenty of shine still on it also.
I know it was stated that paint thinner is not for enamel, and I do not disagree, but I have had no issues with what I am using.
As for what I use, I use Valspar hardener and Klean Strip Green paint thinner. The reason I use this thinner is because it has almost no odor, does not bother my skin, and cleans my painting tools real well.
Some strong smelling items (like fingernail polish) will literally take my breath, so I have to be careful with what I use. Breathing comes in handy sometimes! LOL.
I do experiment with different amounts of hardener and thinner to see if there is any improvement or not, since my painting environment is not always the same. (humidity and temp. mainly)
These tractors are not a $30,000 show piece, so a less-than-perfect paint job won't kill anything.
We all don't have expensive equipment and a paint booth with perfect conditions for painting, so just use patience, do your best, and it will turn out fine.