I've really only used the Ardex K-15 and then just a handful of tmes well spread out over the years. Make sure nothing's on the slab that will impair the bond/bite to the surface. Typically that means shot blasting old scabby adhesives and sealers off or at least buzzing them off with with the diamond wheel on a grinder/vac. Prime it well and sometimes it needs two coats.
Mix with EXACTLY the right amount of water for just the right amount of time and do the successive pours as rapidly as possible so each batch blends into the previously mixed unit before it's settled and beginning to harden. The faster you can mix, dump and smooth out the less wavy the finished product will be. It's doesn't completely self level---------ESPECIALLY if you can't get the product mixed and poured as one continuous "puddle" so it kind of pulls together and settles flat.
Much bigger size jobs really need the pump for the reason I just described. My shop had the pump but we never used it. Coincidentally, the shop owner just sold the pump and a few months later we were pouring about 500 bags of K-15. Man, did we need that pump.
Your job sounds like two guys could easily handle it. Get a mixing bucket large enough to mix 2 55-pound bags at a clip.