+2 Nail Envy. The regular OPI polishes are great, but don’t really protect your nails like the Nail Envy.
I wear white cotton gloves at night when I go to bed with moisturizer. Not to keep the moisturizer on my hands but to keep it off my face - I sleep with my hands on my face and am prone to acne.
I do find that one night with Neutrogena Norwegian Formula and gloves gets rid of almost any hand dryness I may have gone to bed with.
You can buy the gloves at the drug store (at least at CVS) in the first aid/dressings section. They may look tiny but I have super huge hands and they stretch just fine. I couldn’t wear them as functional gloves (too ill-fitting) but they do the job and stay on all night.
Professional manicures saved me, and they’re not that expensive. Avoid gel nails at all costs.
Biotin: 7500 mcg/day. It’ll take a few months before the thinner nails grow out, but one day you’ll realize that they’re not splitting and breaking like before.