I have an Abu Garcia Veritas casting rod which I have really enjoyed.  The handle has become unglued from the blank.  Garcia has replaced the rod and told me to keep the old one.  I'd like to repair the old one.  What glue or epoxy do I use?  Any other tips?

What’s loose, the grip or seat? If grip,  what material is it? You’ll want to use a liquid adhesive epoxy and a syringe. Drill two small holes into the void area (one to inject and one to allow air to escape) being careful not to drill into the blank. 

Get yourself a pin vise hand drill bit set like this:

https://www.amazon.com/Pin-Vise-Precision-Jewelry-0-6-3-0mm/dp/B07FJ6VD2P/ref=sr_1_1_sspa?keywords=hobby+drill&qid=1574872643&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyNDJUTTI3RzVDWlE4JmVuY3J5cHRlZElkPUEwMTA1MTI0MUdSNkVUQ0FOS1BWVSZlbmNyeXB0ZWRBZElkPUEwMzgwODQ2MjFTQk5XV01JVzBGNyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

Gives you a lot more control when drilling soft materials so you don't go too far and get into the blank.
 

I use a syringe that I filed the needle tip square. If you want to re-use it be sure to run a healthy amount of alcohol through it to flush out the epoxy.

https://www.amazon.com/Pack-Syringe-Applicator-Refilling-Measuring-Dispensing/dp/B07PR27S76/ref=sr_1_2_sspa?keywords=syringe&qid=1574872712&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyUFA1V1haNVcxQUpZJmVuY3J5cHRlZElkPUEwMjU4NDEzMkRMUklDVlVQUkZWRyZlbmNyeXB0ZWRBZElkPUEwNTE5Mzc4MVdVREZVTzVQWU04OSZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=