If you use a Pyrex mixing bowl, you can easily see that all of the gelatin, including what's onthe bottom, has dissolved.
If you add the alcohol to the boiling hot Jello and water mixture, all the alcohol will just evaporate because alcohol has a lower boiling point than water.  Be sure to allow the Jello/Knox/water mixtureto cool to about room temperature before adding the alcohol.  About 20 minutes in the freezer usually cools it sufficiently, butbe careful!  If you leave it in the freezer for 30 minutes, it'll be too late to add the alcohol, andyou'll be stuck with a rubbery mess that resembles Jello-flavored latex.  Be very careful never to allowJello to freeze.
If you put the Jello in the freezer to cool it prior to molding, place a hotpad underneath the bowl of Jello. Otherwise, the bowl's contact with the floor of your freezer will chill the bottom of the bowl quicker than the rest. You'll end up with solidified Jello at the bottom of the bowl while the rest is still liquid.
Want to speed up the cooling process?  Keep the pan and the alcohol in the freezer untilyou're ready to use them.
Be sure to clean up spills quickly. No matter how careful you are, there will be spills. Clean them up quickly, because liquid Jello is much easier to wipe up than Jello that has solidified to a countertop, a floor, your cat, etc.