have a problem with wiper linkage bushings

I am having a problem getting the linkage bushings to stay on the pivots. is there a secret to this. I have tried 2 different bushings and they keep popping off. I have drilled a little hole in the back and put grease on them. do you need to snap them on with pliars. should they just snap on with your hands. do I have the wrong bushings. I am having the same problem with the 73 Dart Sport and the 76 Duster. I first used the Dorman part # 49440 bushing. That didn't work too good. I ordered the 3799089 ones and having the same problem. can someone help me with this. have you had this problem before. I am about ready to drill the pivot out and install a bolt with a nylon nut on it.