I can not imagine ever drawing with the mouse ever again. I never could really, i did some half-decent coloring when i didnt have a tablet yet.
Once you go tablet, you never go back. Mouse is a silly inferior tool not meant for art making. It also like, hurts your hand.
EDIT: and to say something extra about Tiki's remark about using small brushes: lies. Use the biggest brush you can but still obtain detail. It'll make colors smoother.
Especially when using a mouse: (in Photoshop)
Use the "Alt" key while using thr brush tool to swap to eyedropper. Crucial for color blending.
Alternate your brush size constantly with hotkeys. Wich are either "[" and "]" or "<" and ">", depends on photoshops language settings.