1) A regular acoustic-guitar bridge pin works well for keeping the strings on at the changer end. I pre-bend the ends of the string just beyond the wrap, also. Now I seldom have problems with the string popping out of the changer while I'm fiddling with the other end.
2) I cut off a short piece of 5/16" dowel rod and drilled a hole through it near one end large enough to accommodate the largest string I use. After I cut the string to length, I stick the end through the hole so it protrudes about 1/16", then bend it 90 degrees to go through the tuner. For the stiffer strings, I also "pre-roll" them a little. I turn the tuner so the its hole points a bit toward the headstock end of the guitar. This makes it a lot easier for me to get the string correctly started on the tuner shaft. It also ensures that the string past the bend is short enough that it won't scratch up the beautiful finish below the tuner shaft.
The tuners on this guitar are Sperzels, the headstock is short, and the tuner shafts are graduated to straighten out the string path as much as possible. This is all very well, but the tenth string I use on the C6th neck is a 0.070" wound, which is the maximum size that will just barely go through the tuner IF you hold your face right, and there's barely room for one wrap on the shaft....
Since nobody complains, I suppose I'm the only one who has this problem changing strings, but I bloody HATE it!
--Al Evans