I use $2 bills too!The easiest option is to just use poor grammar all the time, so if you screw up, the person has just assumed you've made a grammatical error.
My husband likes using 2 dollar bills. Its caused some awkward moments, one being when we were traveling and a Taco Bell employee wanted to call the police because she refused to believe it was real money...
I've read news of dumb cops arresting people for passing real $2 bills.
Fortunately for me, people have always been happy to get them.
One guy was ecstatic to get a hundred of them all numbered sequentially.