Just thought I would make an update to the method I posted, as I have found an issue with it.
The Gunslick foaming bore cleaner that I suggested still works fine in removing sap, however, some fine "000" steel wool works better than a paper towel, especially after cutting on woods with more stubborn sap, like oak. This also doesn't seem do anything to patinas (cutting oak left some blackened areas on the steel--which came off quickly with my thumb and some red Dremel tool polishing compound).
As far as damaging laha, I have not found any problems, so far.
However, if you use Birchwood Casey TRU oil to finish your handles, like I do, you DO NOT want to get the foaming cleaner on it. If you do, you better wipe it off quickly, because it will start eating away at it.
I found this out on my 18" WWII tonight. Luckily, I have already been planning on slimming the handle down some, which will require me to refinish it anyway.