There's a few different areas of photoshop that the word "mask" is used hehe. What is the situation that yours is?
Anyhoo, I'm not sure exactly what you meant by adding to the mask. If you meant adding/subtracting to the selection after using refine edge, you can just use the quick select tool again, it will just add/subtract to your selection that you currently have. (Holding Alt while using the quick selection tool allows you to subtract from your selection)
If you need a bit more precision or selections with some transparency in them after you make your selection with the quick selection tool+refine edge tool, you can go ahead and utilize the quick mask tool to paint parts of a mask in
And yes, the Quick Selection and Quick Mask tools are two different things