I entombed mine with new after cleaning it. It was a messy job but it seemed to work just fine. After a few days I looked to see how it self leveled and cured and it looks decent enough. And, it looks well sealed so it will be effective.
Scraping and replacing appears that it would have required 10 or more tubes of sealant. Covering over took me two tubes of sealant. The sealant was expensive so I'm glad I didn't have to pay 5x more money to do the job.
2013 Ford F350 Lariat Crew Cab 4x4 6.7 Diesel 3.55 Long Bed
2013 Jayco White Hawk 30DSRE