I've seen gaffers hold up a heavy viewing glass up to check cloud coverage. They've all had a small square of thick black tape in the middle of the glass to cover the sun itself. Still seems risky to me.
Can't recommend looking directly at the sun ever, even through heavy filtration. UV radiation is not good for your eyes and the sun puts out a LOT of UV.
If you plan on looking at the sun regularly, get an official sun filter or glasses. Anything for viewing an eclipse should work but it might be tricky to see thin cloud coverage. And even then, I would avoid looking directly at the sun and looking for as short a time as possible.
As for best brand of gaffers glass, no idea. I'll let those that have more than none make recommendations
Edited by Chris Steel, 08 December 2017 - 12:42 PM.