Most cost effective 3D painter is 3dcoat (also a pretty good modelling/sculpting tool) Best is probably Mari but that is really expensive. ZBrush can work ok for the job if you already have it but not a good buy just for texturing.

As for glowing objects, there are two different things here. One is the light from the object cast on surroundings. This you can do in various ways in Poser eg one way is to crank up the ambient on the object's material and use IDL. You can also fake it with lights in some cases. The other thing is the actual 'glow' (or halo/bloom) that surrounds light sources and objects that are brightly lit. This you can't do easily in Poser. Some people have tried various hacks for it (like using extra meshes) but they are not really very convincing. Your best bet to do it with Poser is to do it in postwork, which is how most people do it anyways, even in high end apps.