Walter has over 1300 fonts on one of his Macs, that's a lot. Not only does it get hard to pick one from that long list, it will also slow FCP down. In this video he plays font wrangler.
We use Font Book here, but mainly to preview fonts to see if they have all the characters you need before embarking on building a large motion graphic. Nothing worse then agreeing on a font with a client and then finding out there is no £ or © symbol!