At the moment I don't have any splits or tears, So for the tutorial I did this on a sample nail with a line drawn to simulate a crack. Next time I have a nail that splits and needs repairing I'll do one on my own nail and update this posting.
In addition to your usual gel manicure supplies, you need some brush on glue, silk or fiberglass nail wraps (I prefer the self-adhesive silk wraps), and very sharp small scissors or large nail clippers to cut the nail wrap.
Using very sharp scissors or the nail clippers, cut a small piece of the silk wrap. Just a small rectangle enough to cover the split and a little bit around it. If you don't have very sharp scissors, the edge of the nail wrap tends to fray and can leave your manicure not as smooth as it should be.
With the self adhesive nail wraps it's very easy to carefully place the piece of silk or fiber over the split, and smooth it down and into place with a dotting tool, cuticle push, orangewood stick or toothpick, whatever you have handy. Make sure the silk or fiber goes right up to the very edge of the nail where the crack is. You can even let it hang over just a tiny bit, as you can file it smooth later.
Apply a very thin layer of brush on nail glue over the silk and let it dry. When it's dry, add another thin layer for additional strength.
When it's completely dry, take a fine buffer block (mine is a 240 grit I think) and gently buff over the repair to smooth it down. Don't over buff it or you'll weaken your repair, just enough to smooth it. You can use a nail file along the edge in a DOWNWARD MOTION ONLY to smooth the edge or side of the nail if you left any material hanging over.
Now continue on with your Gel manicure as usual! Basecoat, color coats, and topcoat. Voila! All fixed!
If the split is very large, I will also add Gelish Structure Gel to my manicure in between the base coat and color coats. Just a thin layer or two is all you need to add a bit more strength. Even without adding the Structure, most of my split repairs last me a full two weeks.
Just remember, when you soak off your gel polish, the repair will soak off too. Either you need to redo it each manicure or file off your color very gently instead. I think it's much easier to just fix the crack again than to file off the color.
Check out the tutorial on YouTube!