Arm Napkin
Using a shirt sleeve, like a napkin, to wipe up a mess of any variety.
Stan's secretary blew him under the desk and he shot a hot sticky nut on her face. Realizing she had no tissue to wipe off her chin, she used his Arm Napkin to clean up leaving it crusty and stained for his upcoming 3 p.m. meeting.
Napkin Arms
Putting your arms by your sides, then raising your fore arms and waving them up and down with your hands outstretched (like so your thumbs are pointing to your eyes and your hands are flat like if you were going to slap someone) saying "napkin" many times. It's used when your hands are too messy to get one yourself, or you're just lazy.
"Napkin! Napkin! I really need a napkin! *does napkin arms*"