That surface scum is supposed to be harmless so you don't need to get rid of it ....
However, the only efficient way to have no scum on top is to draw water to your filter off the surface of the tank. The only way to do this is with a sump setup like the SW
tanks. With an overflow & sump, you can also have a pre-filter up in your overflow, which can be easily cleaned/changed without getting your arms wet. The problem with this approach is that this will involve major modifications to your tanks. However, with multiple tanks, you can set up a single large sump to service a bank of tanks. That will cut down on maintainance, but at the expense of complicated plumbling .... plus you have to design the system right or you risk floods, etc.
BTW - no need for a drain if you can just dump the water out a window. I attach my gravel vac to a long hose that runs out a window to my flower bed. Pwc
's automatically waters & ferterlizes my garden. I refill my tank with a simple hose connected to my faucet. .... no buckets!