A salad spinner will do nicely for water removal. It doesn't get all of it, but if they are placed single layer on a big towel, they should dry quite well. You can then bag and freeze.

I blanch mustard greens, collards, beet greens and kale before freezing.

That's the way I do mine, blanch, chill, dry and bag....I love greens and I raise and freeze lots and lots of different kinds.

Last summer, for the first time, I had planted about 15 areas with mixed salad greens. Bib, red leaf, and many other gourmet salad greens. I actually had way too much and can't freeze these without them turning to mush. I used an Oxo salad spinner after rinsing them off. I don't spray anything and they were very prolific and slow to bolt. I thought I may run out by August, so I planted about 8 more areas with the same mixes. These matured fast and I could pick all the way through September. Had so much I was giving away big 2 gallon zipper bags packed with the mixed greens. My grape tomatoes were late but the pickling cukes were good. The excess of these vegetables also were given away as I just can't live on salad alone every day. This year, I don't plan to plant as many, but will do a smaller planting in late May and another in July. Most were just fine with the summer heat too. I was very sick last summer, and used a 5 gallon plastic pail turned upside down to sit on while I picked. I just grabbed a clump and twist them off. Also added a few broccoli greens for a little tang. These gourmet greens are the kinds you see selling for well over $5 a pound. Everyone was loving them. Using organic origins of fertilizeers for the necessary nitrogen helped quite a lot too. I used fish meal and kelp meal as well as some of the other organic fertilizers.