OK I'll give you guys the full rundown.
Omni 4000: I spray both enamels and acrylics through this brush. When using enamels, I thin with Mineral Spirits and clean with Lacquer thinner. When cleaning, I fill the color cup with thinner and use a pipette to remove the excess paint/thinner mix. I do this until the thinner is fairly clear. Then I spray the lacquer through the brush, backflushing ever few seconds. After that, I remove the needle, wipe it down with thinner, and use a Q-tip to clean the inside of the cup. For acrylics, I do the same, except I thin with Tamiya's thinner and clean with Windex.
Paasche VL: Again, both enamel and acrylic go through this bad boy. To clean, I remove the color cup, clean it well, then I use a Q-tip soaked in the appropriate thinner and clean the area where the cup meets the body of the brush. Once that is clean, I attach the cup and run thinner through the brush, backflushing every few seconds. Then I'll take the needle out and wipe it with the appropriate thinner.