What's wrong with letting the liquid escape? The liquid is good! When I freeze sweetcorn, I slice through just the outer part of the kernels, and then turn the knife sideways and scrape to release the rest of the delicious gooey liquid inside them... I'm not particularly fond of the flavor or texture of the cob-side anyway, and the creamy result can be packed and frozen with a minimal amount of air.
I highly recommend using a chef's knife instead of a paring knife though. A big cutting board and a bench scraper also come in handy. If you're doing a lot of corn at once, a baking sheet works well to catch the juice.
Growing up, we'd get a bunch of people together and do bushels of the stuff in an afternoon - cooking, icing, cutting, scraping, and packing simultaneously. With a bit of practice, you become quite fast at it.
But, if you're simply looking for a quick way to process the ears alone, there are specialized tools made for this job: search for corn creamer or corn cutter.
You could probably use a mandoline as well, provided you're able to adjust the depth of the blade. Frankly though, this seems cumbersome. Practice with the knife...