Here is a tip,
If possible, wedge the cracks open just the slightest bit. Apply the liquid accra-glass, and then use a can of compressed air, with a small straw nozzle on it, to gently blow the accra-glass deep into the cracks. Then remove the wedges. If possible, use some type of clamp (such as a padding your stock, and gently using a carpenter's clamp on the outside of it) to apply a small amount of pressure to close the cracks, during the curing period. If you don't have a clamp, then even multiple strong rubber bands will help if you put them in the right place. Let the whole thing cure for three full days before you remove the clamp.
One problem with accra-glass though. If the weather is really hot and humid (such as in Memphis, Tennessee during June, July or August) it is NOT going to cure properly. I don't care what the label or instructions say, this is based on my personal experiences. So wait until you have some nice 70 degree weather with low humidity, such as September or October.
If you follow these instructions, then I think there is a really good chance that your cracks will be permanently fixed. At any rate, it sure won't hurt. Also, even if the walnut color of your accra-glass doen't totally match the wood, it generally blends in very well, and just looks like a normal grain pattern in the wood.
Hope this helps.
Best Regards,
Big Paulie