I ran into the same thing with a cheap starter set. The paint skinned over in minutes and turned muddy when I tried to blend. I fixed it without buying anything new by changing my setup. I made a stay wet palette with a shallow food container, a layer of wet paper towel and and baking parchment on top, then snapped the lid on during breaks. I misted the surface now and then with water and when I did not have a sprayer I just flicked a little water on with my fingers. That kept the paint workable for hours and sometimes the next day. Working in smaller sections and pre dampening the canvas with clean water helped the blends a lot.
The watery feel came from me adding too much water on the palette and using raw paper that sucked the moisture out, so I started mixing longer with just a few drops and I brushed a thin coat of the same white paint I already had over paper first to seal it. I also kept a second jar of clean water to re dampen the brush instead of over thinning the paint, wiped the ferrule often, and covered the palette with plastic wrap when kids were near. The brush sets that came in the box felt rough at first, but a wash with warm water and a tiny bit of gentle soap, a careful trim of stray hairs, and drying them flat made them usable for smooth strokes. That combo solved the fast drying and blending issues without a new purchase.
