Firstly, I agree with teedub and Eddie Winslow 100%. I'll just expand on their thoughts and add my own.
OP, you're thinking way too much into this and also worry too much about who, when and how to approach. This will cripple your results. So fix this first.
You don't have to avoid sets altogether. They can be good practice sometimes and can help your flow. Their rejections will also make you further resistant to rejections and will test your confidence more in my opinion.
Follow steering wheel mechanics well. There's a podcast I did with h3ltrsk3ltr (link in my sig) and some information in that thread.
8 hours is plenty of time for 10 approaches but again, get in the mood, talk to people and do shit. If not you will lose the vibe. My buddy Dantes is one of the best at Daygame. Some of my best wins have been daygaming with him. Read his posts and threads on approaching and game. He's as good as they get in daygame. Find a wingman or such a forum member and hold each other accountable. It will make you feel more like a warrior and a man.
Last but not least. Dress the part. No need to be obscure but also no need to look like Mystery. When I was active, I used to suit up. That was my style but for me it fit my vibe. Do the same if it fits or find your own vibe.
Do you lift? If not, start asap. Some type of exercise is bound to give you that extra boost.
Bonus tip: I said this before. If you are approaching a girl in the supermarket, don't do it immediately. Wait 1 to 2 minutes to observe anyways but when you do, go indirect. Reason being, there may be a boyfriend or husband around.
Please report back. I would love to see your progress.