First make it easier on yourself and work with a 1:20 solution.

1/20 should be bleach = .05

6 gallons water X .05 = 0.3 gallons bleach

0.3 gallons = 4.8 US cups which you can round up to 5 cups.

So, 5 cups bleach with 6 gallons water.

As far as alcohol and the filter, do the best you can pouring it through and rinsing well.