Flattery will get you everywhere.

[Because calling him an old snake is clearly flattery.

Crowley draws his hand away from Aziraphale's cheek, taking the angel's hand with it. A slight movement has him holding it gently, so he can draw it down for a kiss to his palm.]

I know it's not — easy, when we're like this. [Aziraphale was made to protect, and being human makes that incredibly difficult. Especially with all the danger here.] If something happens again, I'll tell you, yeah? No more secrets.