The first thing I did was get rid of that filter in the funnel. It seemed to slow down the process without being 'that' fine a filter. I use the filter from an expired coffee maker that is a really fine grain membrane. It is no slower than the stock filter in a funnel, it will not rip apart as paper and it is simple to clean by inverting and spraying under a stream of water and one can be used for years.
While it will handle 8 to 12 cups at a time, a gallon of liquid may prove tedious.