Have you been thought "hot oil treatments" ?
I took a new manicure course last month and was thought this is the best solution to help extremely dry and/or hard cuticles. Using a mix of almond and olive oil, add a drop of scent of your choice (I chose orange), warm it up a bit in microwave in a small glass bowl/dish. Then dip some cottons balls in the warm oil, place over your nails/cuticles and wrap in foil. If you have a magic/warm bag you can place it on top and wait 10 minutes. Then remove.
Should do the trick. It's worked wonders on me so far, can't wait to try it on clients (they all have great cuticles, I guess I'm lucky?).
Continue to use your solar oil 2-3 times a day.