Makes ZERO sense to counterfeit ONE dollar bills.
If you bought something for say even $80, you would draw unwanted attention to yourself and the bills counting out EIGHTY bills!
The only way to not get caught, would be to spend them exclusively on lap dances.
Go to 4,500 non-chain convenience stores (about 100 per state, easy to find), give them each 200 $1 bills for $100, let the stores spread them into circulation. With connections with cartels/gangs, it would be very easy.
What about using them in vending or cash machines. Somebody had a specific use in mind I am sure.