Smoothed out final casting flash from right case top and experimented with scraping off gasket material using an Xacto #11. This worked okay but was both tricky and higher risk than I like. The blade got caught up on every bit of metal out at the edges and is definitely sharp enough to gouge the parting surface easily. Tomorrow I will try the utility knife blade scraper suggestion. Of that doesn't work I will go back to using my stash of old credit cards at scrapers.