In English Drama Movie: Short Term (2013), Grace say this words to Jayden about her mom's boyfriends.
Whenever I was drawing portraits of, you know, those guys, I would always take forever. 30, 40 minutes just stringing them along, saying, oh, I've just got to do a couple more shadows, or, I'm just fixing the nose. I don't know why I did that.
couple more shadows is it means shadow or Is it idiom?
Another doubt is What does mean by "stringing them along" ?
I am so confused. please explain this lines.