I super glue 3 silk nail wraps together, the result is easy to file and shape, and only a little harder than an actual nail:

• Buy these along with the kind of super glue that has a little brush applicator.
• Trim the nail wraps to about the right size of your nail, but longer then they would need to be.
• Glue them to your fingernail, one by one. Wait about 10 min in between gluing each one so the glue has time to set.
• Shape an file your new 'nail'

These silk wraps are also super useful when you get a fracture in a nail, just glue a wrap over it. (works better than tp IMHO, haha)