remove the oldones and put on the new ones. works fine

Never removed the glue on the bottom of mine, just put the new ones on, never had a problem =D

The alcohol would be used to remove glue residue, you can use any dissolvent for that, or your fingernails or whatever.

You could also temper with the lift-off distance of the mouse by putting something under the new glides, or put them on top of the old ones (then the lift-off distance would reduce, but maybe also the tracking performance of the sensor, so that's trial and error).

frankly hyperglides don't include the alcohol swab anymore. the new ms-3 models are thicker than the old ms-1 ones and are to be used as replacement. you will probably get tracking issues if you put those on top of the old ones.

never had tracking issues with putting the older ms-1 hyperglides on top of my old feet though.

Just use something like white spirit, when degreased it will stick better. Would not put it on top of dirty old mousefeet.

use vodka

There is actually an instructional video on how to install hyperglides!

http://www.youtube.com/watch?v=9aJt9Ei1HXo