Welcome to TVPaint Community forums !

I've already animated a camera but I'd like to continue fleshing out the animation. The problem is, I can't find any setting that'll allow me to hide that grey overlay shown in pic 1.

I am not sure, but I think you need to select camera tool>comands>rest...

bottom right of your canvas is a dropdown. uncheck the Show Camera and I think that should work

you can also do Windows > Show > Display Settings and you can drag the Viewfinder slider to 0 or however much you want.

Thank you so much