Rusty finger
Brown tint of fecal matter found on the tip of your finger after itching or playing with your anus. This is most commonly observed and then sniffed.
After a short jog, Jimmy reached down his sweats and scratched his anus. When he pulled his hand back up, he had a rusty finger, then sniffed it.
rusty finger brush
The art of fingering your butthole and then using your rusty finger to brush someones teeth. - Jim Williams
My wife loves my rusty finger brush. The rustier the better.
Rusty Finger Puppet
Like a rusty trombone, but somewhat straighter. Performing anilingus on your woman whilst diddling her vaginal canal. Classy move, and lets her know hepatitis ain't no thing.
Although I enjoyed that Rusty Finger Puppet last night, you might want to get a blood test.