not quite sure where the hammer beating fits in here.
having worked in the back of a shop as a rental/repair tech, we used a citrus based wax remover to clean off the bases of our skis and snowboards. this has already been mentioned
pour some out on the base directly, then wipe it across the base with a towel or a rag until the entire base has an even coat- in the areas where the duct tape has stuck, you can probably spend a little bit of time rubbing with a bit extra of the base cleaner, it won't hurt.
warning- the citrus base cleaner will help extrude like.... almost all of the wax from your bases. you'll need to let the skis air dry and then give them a good waxing after this is done if you expect them to move on snow.
for wax, spend the 10 bucks to get an actual skitech waxing iron. normal clothing irons do not heat uniformly across the metal plate, and as such you'll have parts that burn the wax, and parts that don't melt it fully like right next to eachother. unless you live somewhere exceptionally cold or warm, you will be fine with an all weather wax.
drizzle some onto the entire base of the ski (less is more in this case, because you'll have yo scrape it off later), then use the iron to spread it evenly down the length of the base.
let dry, and leave it on the ski a few hours (or preferably days), then scrape and brush.
when brushing, go from course to fine in terms of grit. this should be common sense as to why.