This isn't really my first tutorial, but all the previous were awful :'D English isn't my native language, so I'm very sorry for some mistakes and typos. I plan to make a russian version soon, please wait for it ^^
ehh.. it's difficult to explain it even in my native language.. what should i do..
okay. when you use opacity lock, the borders of colored object are fixed - so you can do some kind of shading/color change without worrying about going beyond the boundaries. smth like this, haha, i hope my explaining isn't totally awful :'DD