I think the best advice I can give you is not to let your expectations get too high if you're working with violin samples. Some instruments translate OK into samples, others don't. Violin's in the latter category. If you want them to sound anything like the real deal, be prepared to work like a bitch. See, when a violinist plays a phrase, the notes tend to 'run in' to one another - not like a piano, where usually you hear one note and then the next, and there's a definite cutoff between the two - the violinist generally slides his or her fingers from one note to the next one. Which is why it rarely sounds natural when you try to play violin parts on a keyboard. A good basic strategy is to apply some reverb to your samples. From then on, you're on your own, because I'm buggered if I can make convincing loops of out string samples