I have reached in with a small diameter allen wrench or punch to depress the spring loaded valve in the one way fitting to release pressure. With such a small volume of air, not much worry about a huge jet of air coming out, but still go slowly. You can just tap it a few times to release small bursts.
I try to remember to never release a QD connector unless the sliding collar is very loose. Fortunately none that were under pressure ever gave way.
As for male QD connectors that are too tight of a fit on some female QD connectors, I spin them in a drill with some wet dry sandpaper to radius the sharp edges until they connect easily in the difficult connectors. None have ever leaked on me in the connectors that were not a difficult fit before the modification. Go slowly and stop as soon as they connect smoothly. Clean off all sanding residue and give a light coat of O-Ring grease.