No bar needed, the air gun can spin the Allen key bolt off.
Remove fork & drain oil, refit spring & end cap, air gun Allen key bolt off, strip forks. Fit new seal assemble fork with spring & end cap (with no oil) tighten Allen key bolt.
If the Allen key bolt starts to turn with out tightening up, turn the fork upside down & push down on the bottom fork leg compressing the spring, this will preload the dampening rod & should stop it from turning, allowing you to tighten the Allen key bolt.
Once tight remove end cap & spring, set oil height.