yea a slide hammer is the best way/easiest way
i used to have one at work,,,,,,
find an old nut that fits the injector top where the line threads on
you may be able to make a slide hammer with stuff laying around the garage,like a threaded rod,with a nut welded on the end(that fits inj.)
and use an old wristpin for a weight,with a nut on the top for a stop