Is there some secret to installing injector O-rings?

I've had my truck apart twice now and can't manage to get them all to seal.
Last time they held about an hour and then one let go and started gushing gas.

I'm thinking it's a problem with the aftermaket O-rings. I mean, how hard could this be??? I'm getting some from Toyota for round 3

If there's a trick to installing these can someone fill me in?

 

It's a 22RE

 

my trick is to rub a thin layer of grease or engine assembly lube on them, then be extra gentle. haven't had any trouble with aftermarket o-rings.