Are you using a disposable adult depends, TENA (whatever brand)? Most of the brands have an overnight product that can be a life saver. The bladder training of every two hour toileting can really work. If your mother is ambulatory would she be able to get herself up and use a commode or the bathroom using an alarm. This would help you get your rest and her keep her independance.
otherwise, Iwould make my own underpad using a waterproof fabric and several layers of flannel. I would use a cross stitch to quilt the layers together. Make it big enough to cover the bed from midchest to knees. If it comes to a point when you have to turn your mother while she is in bed, the pads make a great turning sheet so you are not pulling on your mother.
The protective coat for the skin is a great idea especially if she is going in large amounts. They have some that are just barrier cream or lotions, they are clear and just are barriers to prevent breakdown. If she has a rash or irritations be sure you use medicated ointment. There actually is a product that is Butt Cream, first time a Dr ordered it I thought it was so funny. Litttle minds are amused by little things.
Look up incontinent pads on the internet and contact the company, ask for samples to help you make your decisions.
Good luck and remember it won't be under control overnight- LOL