If you're talking about CE2/3 style clearomizers just turn them upside down and use a syringe to suck out the e liquid from the hole you fill them with..you can also suck most of the e liquid out of a poly-fill carto with a syringe too but you don't have to turn it upside down.
IDK about getting rid of the metal taste besides washing them out maybe (if there is still a metal taste in the e liquid there probably isn't anything you could do)..I pull my CE2's apart and clean them all the time..if they are CE3's they can be a lot harder to put back together. If you look in the
Clearomizers section you could find more help with cleaning/pulling them apart..also if you search YouTube you can find a lot of videos there.
You can use a
tank on anything you can screw it into and if it doesn't screw in you can get an adapter for just about anything..sometimes I even use a tank on a slim 510 auto battery...