I use lemons in my kitchen for cooking almost everyday and I really enjoy half a lemon squeezed into my water. Needless to say, there are juiced rinds of lemons around almost everyday and it is the best thing that ever happened to my nails.
I have never had super nice nails, I have been a gardener as a profession for 8 years now and I don’t care what soap you use, the dirt never seems to come entirely off. Enter lemon juice, the best cleaner I have found for my hands. I use a reamer to get the juice out for a recipe, then instead of throwing the rinds away, I keep them to clean my hands and nails after any sort of activity involving dirt.
For cases involving machine grease, I juice half a lemon, add it to baking soda and use that to scrub my whole hands. It removes all embedded dirt and grease, leaving your hands clean and your nails white.
Just as a final note, it really stings if you happen to have any cuts and scratches on your hands but it helps disinfect them as well. After a thorough cleaning, I like to rub coconut oil into my hands. I have used this method over the last couple of years to repair the cracks in my fingers and prevent future ones.