My restoration process is essentially the same for every pen; access the pen, disassemble, clean, install a new ink sac and reassemble, yet no two pens are the same.
Gotta begin by examining the pen, determine what it is made of, look for damage, tooth marks, and other potential problems!

As the pen is being disassembled I put all the parts into a clear plastic box that latches, accidents happen and losing parts is avoidable. Plus the box is only 99 cents at Michael’s.
The process starts with the nib and feed. I learned the hard way, that water is bad when the pen is made of hard rubber (ebonite) and you have to be super careful when using heat on resin. Remove the nib and feed, then use a Sunshine cloth to restore an amazing luster.
On to the section, use a dental pick and xacto knife to remove the remains of the old sac. Review the overall condition of the section, if it scratched, dull, discolored? Normally I lightly go over the section with sandpaper. Starting with the 1,000 grit and working to the 7,000 grit at which time the section should be scratch free and shining like new.
Grab the flashlight and shine it down the inside of the barrel – scary isn’t it? The dried up sac may have attached itself to the barrel and the pressure bar, and will need to be scraped out. Dependent on the filler system and mechanism, I often remove the filler lever and the pressure bar. With all the parts out of the barrel it is much easier to scrape any remaining ink sac off the barrel wall. The Sunshine cloth on used on the lever, snap clip and J-bar to remove tarnish, rust, stains and ink.
Unless the barrel is chased, remove scratches and tooth marks with sandpaper. Otherwise a good going over with the Sunshine cloth will remove grime and restore the shine to the barrel. The lever and J-bar get reinstalled at this point.
The pen cap receives the same treatment as the barrel and the Sunshine cloth is used to restore the clip and cap band.
Time to fit a new sac. How do you know which sac to use? The websites below provide a variety of sacs and charts to determine the appropriate sac for your pen. The length of the sac is based on the inside length of the barrel less the portion of the section securing the barrel. Apply shellac to secure the sac to the section, after a day, coat the sac with talc and reassemble the pen.
I do not apply wax to the pens, I apply a light coat of mineral oil to BHR. I probably should add wax to the BHR pens as a protectant whereas celluloid needs to breath and should never be waxed.