I usually just disconnect the hose before the fuel pump and let gravity do the work. Put a 1 gallon ice cream bucket under there to catch it and use a vise-grip pliers for a shut off.
If the lines are blocked or broken then just run a hose down the tank inlet and siphon it out.
You can get a hose with a bulb to prime it at most Auto parts, or Hard Ware stores.

Dump it into a bigger container and repeat.
The filter should be after the pump, unless you have the modern electric pump in tank kind of set-up?