Just a quick little post on how I do the re(re)-basing. Let's start with a old metal Nob that I now want on a 32mm base. I got some 32mm slota bases for just such things.
Free the model from its old 25mm base, this is done by either carefully bending the base until it breaks along the slot, or cut it away if it's stubborn. Glue on on new base!
Plastic boy on 25mm base, that I am going to keep him on. Carefully scrape the old flock off with a knife. Painting over the old flock is really slow and tricky. Plus, the flock I used just drinks up paint, so that is a no go.