It will depend on how big the brass tube is and how plugged up it is with CA. Soak it in acetone for a bit and then run a piece of scrap wire through it to poke out the CA, then soak for a bit more, run the wire through, soak, wire, etc... You'll just have to play it by ear to see how it goes. Depending on how badly it's plugged up it shouldn't take too long. On the other hand, if it's totally blocked off and hard as a rock it might take a bit.

Curious question, is the brass tube a straight piece or is it curved?? If it's just a straight piece of brass tubing that his plugged up with some CA is it short enough that you can simply drill it out with a drill bit??

Ken