I haven't been out much, save limited occasions between shielding and shielding again but I found having the metal bit on masks helped. I'd mould it over the bridge of my nose as high up as I could (while still making sure it covered my lower face properly) and move the bridge of my glasses over the metal bit.
I found mine would only usually fog up if I was rushing and breathing more heavily through my mouth so would try and breath more gently through my nose.
I've seen people say something about cleaning the lenses with something which helps them not to fog up, washing up liquid maybe, I'll see if I can find it (and that it's ok for lenses) unless it's already on another link.