First steps are very important!
How load a brush with paint correctly! Follow 2/3 Rule
A. Wet your flat brush and gently lay flat on a towel paper to remove excess water.
B. Pick up paint by dipping one corner of the brush in one color and opposite corner of the brush in another color.
C. Stroke brush back and forth in a sweeping motion. Repeat step B until the brush is full of paint 2/3 of the way up the bristles. Also the distribution of the colors on the brush should follow 2/3 rules. You should see on the brush more of one (usually lighter) color and less (usually darker) of the other one.
When brush is loaded correctly you should feel like the brush glides when you make a stroke.
When you run out of paint and need to reload just repeat step B but this time dip the corners of the brush in the colors little bit lightly.