Ok, I played around, and let you know my findings...
I've cut off the oxide layer of my potassium chunks, after I tried to lit a piece of potassiu, to see how it would burn. It didn't. I did heat it with a propane torch, but all happend was a controlled oxidation to KOH.
So witha new scalpel I went to cut, it went very smoothly, there was a small spark at one one point which freaked me out, but for the rest it went very ok. I stored the clean chunks in oil, and hope they stay ok there. I had a lot of fun with trowing the pieces into water, I did a fair amount during the day, but kept a bit for the night... Actually a pity I did trow so much in during the day, at night it was absolutely beautifull!! I wrapped the peices in a tissue (not more than ~2grams I think) and they were trown into the water, first is a big puple flame, than a pooof, and then there are 20 purple small flames swimming over the water, sometime a crack here or there... absolutely cool! A friend of mine catched in on tape, I hope to post the video here when it's ready.
I also did a small chunk into water for my family, a piece of 1,5x0,5x0,3cm was thrown into a plastic bucket with some water, but it reacted the same as sodium, a bit fizzing and a puple flame.
From my experiences are the stories about potassium with big explosions are a bit overexaggerated, if the pieces are a bit cut to small chunks they can be safely thrown into water.