after replacing rear brake shoes on my 96 Dodge intrepid brakes shoes make a rubbing sound

I followed instructions in the haynes manual to the letter for replacing rear brakes soes and they still make a rubbing sound after about 10 to 15 minutes of driving also they have a sound when I let off the gas like they are rubbing without even hitting the brake sometimes not all the time when I push on the brake pedal it is firm then acts like it is going to go to the floor but when I let up and push again it gets firm again