Volunteering: Sorry, welcome to the pre-med world... You unfortunately need longevity here. You want to accumulate a few hundred hours over a few years with a weekly commitment. If you quit before submitting your primary application, then you well look like a dreaded box-checker. ADCOMs don't like it, and will make you look bad. If you don't like volunteering, then too bad. It's the price you pay as a pre-med. See if you can do some positive things for yourself during volunteer shifts, like doing school work and shadowing during your shifts. Of course you should be respectful to the staff and do whatever you're asked, but maximize your productivity doing things for yourself.
Shadowing: There is no shame in treating this like a check-box item. Try to get at least fifty hours over mutliple specialties, and you'll be fine. You don't need a ton of hours or a huge continuous commitment.
