Finished product, I love them!
What they looked like when I bought them (two from Craigslist, one from Walmart that is almost a perfect match, total spent: $50)
So. Much. Sanding. Please excuse my dirty garage.
Ended up having to take them apart to sand in the nooks and crannys
All put back together, and I used a dowel (about $4) to fill the bolt holes because they were bothering me.
Moved them into the apartment, used a carpenters square and ruler to draw my pattern on the seats, then started in on painting.
The paint and polyurethane was all stuff I had left over from other projects, so no extra cost.
So. Much. Taping.
I mixed the mint color up myself. I mixed latex and acrylic paints… not sure if that is something you're supposed to do, but it was what I had on hand.