I always use de-waxed shellac flakes ordered from a catalog. I mixed these with denatured alcohol to make a thick mixture, then took some of that mixture and thinned it further with more alcohol. Then I would build up the rim bed with the thick mixture, allowing at least 2 days' drying time between each layer. I'd also coat the tire base tape with a coat of the thin. After the rim bed is suitably built up and dry, a final coat of thin shellac is added to the rim and the tire mounted. Another 48 hours (minimum) to dry and then the wheel is ready to race. When the tire needs to be replaced, it is removed with a thin blade screwdriver - done carefully, there will be no damage to the shellac bed, and the new tire can be installed after the two coats of thin shellac, as described above.
Now, after having written all that, I'll say that I would probably not bother anymore. The Vittoria is a really good glue, and probably sticks better than the best shellac job. The only time I would consider shellac now would be for elite-level pursuiting, where the slightly lower rolling resistance offered by a shellacked (rather than cemented) tire might conceivably make a difference - and even that's grasping at straws.