Dont listen to that
Plenty of texture artists use their mouse.
You just have to learn control to reduce those shaky lines
Also this is cool for a second head.
Don't draw textures with your mouse. You can use the pen tool on Photoshop for those lines makes it look much better!
^ Bad advice. It's fine to use a mouse. Graphic tablets are better, of course. You just need some practice over mouse control to draw more steady lines. Personally, I draw with a trackpad. If you want to draw straight lines, hold shift and while drawing. Keep practicing, you'll get the hang of it.