Adding a quick glow effect to an object is easier than it may seem. The most important aspects are...
1. PUT IT ON A DARK BACKGROUND. It's *really* hard to make something glow if it's on a light background. It's a light source! So it should be lighter than whatever it's on.
2. Boost saturation. This is a rare occasion that I paint with 80-100% saturation.
I also like to selectively soften some of the object's edges, especially wherever the edge is almost white. It gives it a nice subtle bloom effect that really helps to communicate the glow!

(You can view a higher res video here on Twitter)