It's a process for me, I open hundreds of tabs, save all URLs, strip trackers from URLs, remove duplicates, then I reload all tabs into a fresh, empty multiaccount container, then I use a scraper addon called gatherfromtabs to pickup all the prices, then I log and setup everything up to the last page of the sale, I tally up all the totals in excel, order by price, usually 100s of ads, find the absolute 3 cheapest ones, review the ads really thoroughly to avoid scams and then buy 10-20x of whatever this item was to make it worth my time.

This process will become more difficult over time.