I use Kiss New York's Diamond Hard Strengthener Nail Nourishing Serum whenever the tips of my nails break easily or my nails become weak after getting gel manicures. It strengthens and protects my nails. You just need to apply it 1-2 times after removing oil and moisture from your nails, but I find that applying it for about 2-3 days makes my nails hard and prevents them from breaking easily, so I use it consistently. It applies smoothly, feels cool when applied, dries very quickly, and has a slight scent, though not strong; it feels just like regular nail polish. As for a tip for applying the nail strengthener, apply one coat first, and if your nails are very weak, apply another coat. Do not remove it the next day; instead, apply one more coat. Then, remove it the day after that and repeat the process. I think it is best to use it correctly based on the tips I heard. As a nail nourishing serum, it is affordable and comes in a large quantity, so it lasts a long time. Overall, I think all Kiss New York products are good.