I have used That sherwin williams finish for a couple years.
It is extremely finicky.
I tried mixing it the way wes did, with the syringes, but that was my problem all along. I used an entire gallon before i figured it out.
It kept spraying terrible and full of fisheyes, like it was contaminated.
I then mixed it by eye in a mixing cup instead, and it sprayed perfect. The syringes were melting and contaminating the mix.
I used it for about a year and a half after that, mixing it by eye and it worked perfectly fine. It wasnt even that demanding of exact mixes.
But man, that was the hardest year/ gallon of my finishing experiences. I eliminated every single factor that was causing the contamination, and of course it was the very last one.
I never had a problem with it sagging or anything like that. Teh weather is so dry and hot here, that when i would spray a coat, , 15 minutes later the previous was dry to teh touch and dust free.
I did eventually end up with a problem with it cracking though. I dont know if it was because of the old catylst or from too many coats. But it cracked from the inside out until it looked like a broken mirror.
It also didnt cure in 24 hours like wes' seemed to. I still had to wait 2 weeks for it to fully dry to where it wouldnt shrink back after buffing it.
Just some info about my experiences over a couple years with the stuff.