Halloween latex/makeup questions

Hi,
So my son's school changed the rules this year...nothing covering up the face "no masks." Wel he was going to wear a helmet that goes with the eva foam armor on his suit.
So if we were to use makeup...and or latex (another skill I need to learn....yeee!) Is there a good place to buy latex relatively inexpensively?

I see tiny bottles...but that is it....I would need to (somehow) make a jaw/mandibles (think praying mantis) and somehow ancher this around his mouth.

ANY/ALL suggestions on materials and even how to color/paint the face and prosthetic would be helpful.

Thanks!