Actually, the pressure is the same with piston almost out or all the way in, pressure figures off the OD size of the piston itself, VOLUME is what changes, pressure stays the same. Still, a good idea, once broken loose EITHER way they always get easier.
Instead of ruining what may be a rare hard-to-find banjo bolt you can match the bolt to a common metric bolt and drill that to make a custom grease fitting too, what I did last time. Make it a lower property class number (8.8 vs. 10.9), it makes it easier to drill.