Most people generally have a set of companies that are ideal for them in a tier'ed manner. In that case, more efficient way would be to choose ~5 companies, do a lot of homework about their business & write to key people at these places telling in ONE paragraph what you can do for their business. If it fails, choose next ~5 and so on.
It falls somewhere in-between spending 10 hours of effort on 1 application & mass applying to 50 companies without any effort whatsoever. This is also how effective sales teams work.