I am far from an expert, perhaps that is why I am always afraid to "open up" a crack.
I have in the past used accraglas, and a heat gun (hair dryer will do fine). I put the glass on the inside of the forend and hit it with the heat gun. It will run and leach into the crack. I wipe the excess off the outside and call it a day.
If the crack appears to be open I wrap electrical tape (sticky side out) around the piece to hold it tight until it sets. Just make sure the glass is wiped off good underneath the tape.
Let it sit to dry with the finished side up, so gravity doesn't pull any of the glass out onto the finish.
This has worked on some pretty nasty cracks for me, your mileage may vary.
CHAZ
