What we do is buy the gallon, plus three 2 quart containers and 3 pint containers, all relatively clear. Pour the gallon mixture into 3 equal parts, and then do the same with the catalyst in the pint containers. This way each mixture is equal, and there is no guesswork on the mix. I saw a guy get it wrong. It smoked, but didn't light.

Mix the first batch, pour all around on the bottom, and spread out with a throw away brush. (Harbor Freight has good 2" brushes for less than a buck.) When that batch starts to kick (react and harden), start brushing on batch #2. When batch #2 kicks, mix batch #3 and be done.

Mechanical bond between the first layer and the original coat, and chemical bonds between each successive layer.

Also a big fan of taping it off, like Rog.