Ray,
You can not "go down past the stress cracks". If you go that deep you will have removed the fiberglass from the limb and ruined the bow. The challenge in restoring these old bows is to stabilize the cracks then find a solution to bringing back the beauty of the bow. Dark colored glass is easier to work with because it doesn't show the discoloration inside the cracks as much. Covering them is sometimes as simple as going over the cracks with a colored pen and then putting the finish on. There are no pens that I know of that can match the color on these limbs and if there was one it would still look terrible because of all of the little brownish colored fibers mixed in with the green. I suppose there are ways other than painting the limb such as adding a colored stick- on such as the fake snakeskins for bows but then you have to take what is available or pay big bucks to have some made in the color that you need.