This is a good article on how to use it for belgian bottles: http://byo.com/stories/issue/item/1886-corking-belgians
Make a small mark with a sharpie to indicate which base slot works best on a typical 750. They can and do vary in height so check your bottles beforehand.
The most important part of all is to keep from breaking the flexible channel/funnel when you are retrieving your newly-corked bottle. As mentioned in the article, remove the base, hold the bottle neck and lip with one hand and apply the full range of the plunger to push the cork the rest of the way out. Use the hand holding the bottle to reinforce the plastic channel, keeping it from flexing as the cork slides the rest of the way through.
I have found though, without something to fit between the plunger and the top of the cork, it is very tough to free the corked bottle. I use an inch-long piece of wooden dowel for this. As soon as the cork's been driven into the bottle and the base plate is removed, rest the dowel on the top of the cork while holding the bottle & supporting the surrounding channel. Swing the plunger and out pops bottle. Easier than it might sound.