On my first night at Likely Place, I tried to take sky flats, but unfortunately, the sky wasn't clear but some clouds were in it (which disappeared later on). Second evening looked the same. And then I remembered Richard Crisp's way of doing sky flats. He does them during the day. Puts several layers of white cloth (clean T-shirts) over the scope and covers the back with aluminum foil to cover any light leaks.
Well, the T-shirt idea sure became handy:
The flats turned out great! The T-shirt also helped with the Luminosity flats who often get some stars into them as they have to be taken very late.
... though the rest of the night sucked: many, many clouds and in the morning it even started to rain lightly (before I could cover the scope!!!)