I haven't done it, but the hydraulic cylinder I got recently to build my 50ton press has a hydraulic return/retraction.
It is effectively a small separate hydraulic circuit with its own hand pump. The outside space between ram and cylinder is quite narrow on mine - maybe 1/4" or less, so it can;t contain much oil at all. They put a small hose fitting just at the end of the stroke and connected that to a 1" cylinder with a lever. Returning the ram only takes 1 stroke of this lever. There is no reservoir as such, I just filled the cylinder with ram fully retracted and the small cylinder fully pushed in (retracted) and connected the hose to it. There will be a few bubbles in the oil now, but that doesn't matter really. Seems to work well.