Lookin' to improvise like David G., eh? Well, it isn't that hard, and here's why:
Gilmour uses the pentatonic alot, I'd almost say mostly. But what adds that punch, that "movement" to his solos is this- he follows the chord changes in his solos. Say, for instance, you are playing out of e minor (let's use "learning to fly" as an example). The rhythm/chord playing under the outro solo is a simple alternation between e minor and G major. That's it- 2 to 4 bars of e minor/G major.
So, you would want to play in the e minor pentatonic. When Gilmour looks for something to put in there, he may outline the a minor chord. If you look closely at the e minor pent, you'll be able to see the shape of the a minor triad (a,c,e). This isn't the same as playing in a minor! It's just highlighting the a minor chord in the e minor pent scale, and just for a bar or two.
If you look closely at Gilmour's solos, all of them, you can see the "outlines" of several chords in his phrasing. That solid sound to the solos is actually the sound of playing chords in his solos, not the scales themselves.
Let me know if this helps. There are some other tricks he uses that I would be glad to share.
Michael