I've had some fancy magnetic scrapers over the years, but my go-to device is a simple 4" paint scraper with a single edged blade. I used to get frustrated that even if I rinsed and dried the blade carefully it would rust quickly and no longer be sharp. I realized these blades have a thin coating of oil. Now when I'm done I remove the blade from the scraper, rinse, dry and then apply a thin coat of cooking oil and then put into a ziplock bag. Now they work for 3-4 scrapings, becoming a completely trivial expense. Just remember to wash the oil off the blade before you use it each time or it will likely shutdown your skimmer for a while.