I have a Finish Line gun and love it, mainly for the "bag" system
it comes with. I don't know if they are all like mine but putting a
bag in the cup and sealing it shut is great.
You can use 1 quart freezer bags by Zip-Lock or buy the ones
like the kit comes with.
You can really shake it to keep it mixed and even spray upside down.
I have an Astro gun that sprays better and cost a lot less, and
now you can buy a liner kit like the Finish Line one that is universal
with different adaptors. Since I got one of these and have the bag
system for my Astro I may never spray with anything else.
It really makes clean-up easy too.
The only advantage of the Finish Line one I have is it uses less air
than any of my guns and sprays at a lower pressure, it works
good at 25 PSI.