I looked it up the other day and loads give recommendations for a 15% glycerine solution now and that a 50% solution causes more lag when growing it up.
Ok - I half way fill my little jars with 50% glycerine, 50% water and put the lid on but just slightly loose, then put them in the pressure cooker on a trivet and cook the buggers for 15 minutes or whatever. Open the cooker, shut the lids, that's them ready to use when I need them and they go all vacuumy and make that shhlunk sound when you open them.
Then when I've made a yeast starter and cold crashed it I use the handle of a spoon to get some yeast, put it in a jar, shake the bajeesus out of it so it's all homogenised then just shove them in the freezer. Mine doesn't have a defrost cycle so I just leave them there, but people who do put an ice pack freezer block thing in little cool bag with them so they stay frozen when the thaw happens.
Then when I make a starter I scoop out a bit of the yeast and use that - I don't even use the whole jar and get in one step to do a 23 litre batch. I should step it up, really as I've just been going straight into doing a full litre on the stir plate.
I'll be making a starter tonight or tomorrow of yeast cultured from Fuller's 1845 that I've got banked.