I too have the same dilemma with not one but NOW two decanters- A Kluk Kluk and FT188. Having also tried the coca cola method and steradent, I took the opportunity to ask both Mark Hill and Ron Wheeler at the glass fair yesterday.
Mr Wheeler suggested "Magic Balls ", which can be purchased from Lakeland for just over Â£3.
I will shortly be placing an order as I have now run out of coke! (Have just filled up my FT188 for the second time!)
Lovely vase, reminds me a little of H Tynell which I let slip through my fingers yesterday, was spoilt for choice..... went home clutching a Mdina Lollipop..... poles apart, I know......