All things considered, their communication skills could probably use some work. But in Crowley being the eyes and Aziraphale being the ears, they're relatively seamless. And Crowley does not seem intent on surrendering Aziraphale's hand. The could communicate privately like that.

Forward, he signs onto the angel's palm. Slow. Table, left.

"The staff are conspicuously unhelpful about this, claiming we've always been this way. Obvious bollocks, I just watch you go blind."