Putting small tip with a somewhat ridged tube on the end of the wet/dryvac hose and shove it into the deteriorated balsa. Then play around with it as a physician does when he performs a liposuction. Just shove it in, move it arund and suck out the balsa you break apart. The tube would have to be somewhat large, perhaps 1/2 or 3/4 inch but it might work if it had a good tip on it.