I use glass chips that I purchased on ebay. I have several 6.5 gallon carboys and it does takes a lot of chips to raise the level up to the top of my carboy. But, I like this much better then adding water or wine.
When it is time to rack the wine, I just gently push my Auto-Siphon down through the chips until the siphon hits the bottom of carboy. As far as getting them out of the carboy, I just dump them into a stainless steel colander. I give them a quick wash in Oxiclean and then santize them. Works great.
Robert