The first step is to ask why. Why are your shoulder hurting? Is it from arthritis and decades of wear and tear? Or could it be from the way you have been working out that has now become a repetitive-use-injury? Either way, you will likely benefit from making a change.
Try some small changes to your exercises:
Rotator cuff exercise can be done at home:
Have a Theraband left over from PT?
Change your position on the lateral raise machine:
Exercise Don't Hurt! 