The EASIEST way to replenish at home is to use XTOL: the developer is also the replenisher.

Mix the 5 liters and decant it. Set aside a bottle that holds enough for you tank. Label it "WORK".
( call it that because you hope that's what it will do !)

To 'season' the Working solution, soak a couple rolls of old film in the solution. Then, follow PHOTOTONE's directions. Kodak published good data on XTOL as a replenisher:

http://www.kodak.com/global/en/profe.../j109/j109.pdf

( the 'seasoning' reduces the activity of the fresh developer a little bit, and in a few rolls you'll balance the pld developer with the new, and development times will stabilize. It can be worth bother if you like putting a little effort into the process. )

Share the results !