Hi all, I saw this thread in my blog stats.
As to getting paint to glow, it's something I've thought about a bit.
Someone mentioned medium above. When you go through the baroque/rococo painting section of the Louvre there is an incredible glow they get with their paint (not the Fragonard and Boucher formula stuff, I'm referring to the naturalistic work). It culminates in the room with Greuze and his student's work. The next room is David and the beginning of the academic painters and the glow is gone. Clearly there is a different medium being used in the 18th century, which the academic painters rejected.
In portraiture Sargent's paintings don't glow like a Lawrence does, and we know Sargent just used linseed oil. In fact if you look closely at a Sargent edge, he would sometimes 'fake' the glow by actually painting a slightly lighter value at the beginning of the background. Rupert Alexander does this well in his portraits: http://www.rupertalexander.com/
For landscape painting, I think the best way to get a painting to glow is to paint looking in the general direction of the sun. It's hard to get a painting to glow if you have the sun on your back.
The English school, Edward Seago, and today David Curtis (http://www.djcurtis.co.uk/DAVID_CURTIS/galleryx.html
) are great to look at for 'glowing' landscapes.