Just clamp the lifter in a vise with a 1/4" bolt or something similar bearing against the pushrod seat. If it's hydraulic it will pee oil all over the vise and the plunger will retract slowly. Don't overdo it on the pressure of the vise jaws.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!