It involves some time,and elbow grease,but its not too terrible.
First decide how long you want it...Find a pre-made cork handle that lenght with a 3/8 inside diameter..Your gonna have to slide it from the butt,so you'll have to shim it with masking tape to fit tight and straight...You'll also need a rat tail file to ream it to fit..
Remove to the old grip by chewing it off with a pair of pliers..Go slow and take your time...Get as much as you can...Then once to the old epoxy and cork leftovers..Lightly sand it off,or scrap it off with a razorblade(without sanding the blank and damaging the fibers)...Sometimes lightly heating it with a heat gun helps...Just be quick and careful with a heat gun..I never heat a blank longer than 3-4 second intervals ..and allow each pass to cool for a few.Again to avoid damaging the blank.
What you'll have to do is use a graphite shaft from either a broken rod or golf club shaft that is close,but slightly under, the diameter of the butt end of the blank..Were gonna need to fit around 6-8'' inside the original blank and shim it to fit with masking tape...Then use a two part epoxy (clubmakers shafting epoxy works great!) and heavily coat your masking tape shims and between them to ensure a solid,long lasting bond.
Let that set up for at least 24hours..Then ream,shim,and install your grip...using the same epoxy...Throw in a rubber butt plug,and you'll be good to go.
I should add that extending the rod will also make the action faster.
Heres a bass pro spinning rod I extended a few years back.
The middle pic is the 16'' of an old pinnacle rod I cut (6'' shimmed inside,9-10'' for the handle) plus a new reel seat.
Once reinstalled..I just re-wrapped everything to hide the ugliness.lol
Hope that helps.
