2. I very rarely create product pages or change them. For the most part, I'm listing against existing, popular listings. I have created on occasion (when the last raspberry pi came out, I bought 10 from England and made a listing and sold quickly before others got stock and the price went down. Something I wouldn't do now, not worth the money for the time, did it to learn. I might buy a couple hundred when the next one comes out and outsource fulfillment though.)

Finding items: I look for items that are already selling well, ideally multiple times a day (you can determine this from sales rank and keepa charts, easy to find out how to read them, use google and you'll find many blog posts). Sometimes I'll look at a store and see which items are good for amazon (enough margin, fast selling, etc) and sometimes I'll look at amazon and then try to find items at a store (when I have an item that does well, I'll often look for other items from the same brand or category.)

I use oaxray, a paid tool, costs $100/month to find products. It searches through a webpage and tells you which products are profitable for amazon, then I filter through those. Recently I've begun training employees to use it and make me lists of finds which I then go through.