We took one of our "between major projects" weeks and cleaned up the entry and living room floors with a good scraping/sanding and a fresh coat of poly.
The bubbles in the old poly had to get scraped off with a paint scraper, it was one of those cases of "it looks a lot worse before it looks better". Brian manned the sandpaper and I worked the scraper. This is a "rustic" floor and it has the old-school nails. All those nail-heads make it so we couldn't use the power-tools methods here. I bet Super Jim could actually have done a good job with this (he's our very trustworthy and excellent wood flooring guy, Noah added the Super to his name!), but we do like to practice a little DIY whenever feasible.
It made a nice improvement! We'll definitely be able to keep this floor off the "do something about it" list for another few years after that treatment.