I've been using normal sandwich bags- 5.875" x 6.5" and come in boxes of 125. I've been doing 50-70 per day for the last ~4 days, with a few more days to go. It is a bit time consuming, but half the time spent is just thinning the fruit.
As Alan mentioned in the thinning thread, it is probably a good idea to start on the apples, before moving on to peaches as it can have a bigger impact on the return crop. So most of my thinning has been on apples and pears so far.
I've bagged a few peaches, as it is something I want to give a try this year, after hearing about my dad's success last year. He is using the smaller bags this year, as he had some issues with the bags coming off with fruit. What he got to stick around was perfect. He is saying that he'll re-bag later with a larger bag, but that seems like a lot of work to me. But, he is retired and doesn't have that many peaches to bag (he mentioned ~50 after thinning), so maybe it will work out.
I think the fruit is a bit bigger this year, than some of the past years that I've bagged. Even though we got a late start, there has been a lot of sunny weather. It lead to the first strawberries 3-5 days earlier than normal for me.
I sprayed a single coat of Surround about a week and a half before I started bagging, hoping that it would help me have a few fruitlets without PC eggs to choose from. It kind-of worked, but it is quite a pain to examine each fruit before thinning to try to find the new unspoiled ones. It makes thinning take a lot longer. I also collect the fruit and bring it to the garbage, rather than dropping it on the ground and letting the PC pupate.
In terms of how I prepare the bag, I cut the 2 bottom corners off while they are still in a big stack. Then, a few bags at a time I make a single cut into the zipper, not extending much past it. This cut lets me completely close the bag on both sides of the stem. If you try to do a bunch at once, you wind up making the cut too deep and risk the fruit falling out through the resulting hole.
I just started making the zipper cut this year. I think that this cut will help keep the bags in place. In the past, I would routinely lose quite a few as the season went on. It is also quicker to put the bag on, as I only have to open and re-seal half of it.