Dealing with an older man who is mentally slow?

I know this might sound funny, but if you know some kids- try to see if they can teach him- they may speak to him in a manner more understandable to him- your vocabulary may be throwing him off- and kids can use examples of pushing the button in more simpler terms- or if you don't know any children- try to talk to him in more simpler terms like pushing the button- say like you push the doorbell to ring or push the number buttons on a phone- hope this helps- good luck