You can also avoid the pre-mature micro-set issue if you simply make sure that the decal is pretty wet when you apply it. The water will dilute the micro set just enough so that it retards the bonding process enough for you to manipulate the decal.
The "spit" technique works on the same principle.
I've also found that you can sometimes work the bristles (soaked first in micro-set) of a fine haired brush under the decals if they set pre-maturely. This only works in the first minute or so. After that, you are most likely stuck.
When I'm applying a thin decal with micro-set, I use a brush (dipped in micro-set or water) to manipulate the decal until I get it into a position I'm satisfied with. This also helps keep things lubricated.