I've just started using watercolors recently and I'm having a difficult time getting my shading transitions smooth. I'm using Speedball acrylics for shading/black. I'm also using some cheap brushes mixed in with Robert Simmons white sables on Canson 140lb cold press. So far the shadings been streaky or cloudy looking. Also if I'm painting something with a ton of black, like a panther, it looks streaky. Does this come with practice or do I have something going on in my materials list?