Sorry to hear your first propmaking attempt didn't come out as well as you liked. Trust me, you are in very good company.
If you want the thing to glow, I'm afraid neither thin canvas, nor standard spraypaint are good choices.
When doing a metal frame technique, you're looking to build a composite surface around the frame, that way, it can be rigid but hollow. Unless using fiberglass and an unusually clear resin composite surfaces like this will be opaque, and any lights inside will be trapped. Even thin canvas is generally thicker than ideal for props. If you want to use fabric, you should generally be using muslin (which is thankfully nice and cheap). Then, you don't just apply the fabric. You must apply the fabric after it has been saturated in an adhesive, like white glue (AKA PVA glue) or a thinned starch-based paste (e.g. flour + water). Also important, you want the wire frame to actually be built rather strong, sort of like building a bridge. That way, cloth strips can be pulled rather taught around the structure without the frame deforming.
Once you've got your composite structure built, the next step isn't spraypaint. The next step is to cover up that fabric texture with a substance that can be sanded nice and smooth. If trying to improve your existing prop, I suspect you want to start here. Layers of spraypaint are much too thin for this purpose. Wood putty, thinned paperclay, jointing compound, Bondo autobody filler putty, and repeated coats of white glue are all possibilities. Then you sand starting with 60 grit paper, and moving up to at least 220 grit, 400 is better. While sanding, any time you reveal that fabric layer, you have to add more filler stuff, you can't sand fabric fibers smooth. Once you have a smooth sanded surface, you apply primer, and find all these flaws that you never knew existed, then you either repeat some steps to fix those flaws or you give up and paint. Again, this gives you an opaque prop that won't glow on it's own.
For a good translucent prop (which is what you need if it is going to have lights in it to make it glow), you need to start with a clear or translucent material. Then you need a translucent paint, which is a lot like regular opaque paint, only it has a much lower percentage of pigment in it. You can make it yourself by mixing the color you like with clear paint, though you should research how to do this with spraypaints; getting them out of the can so they can be mixed in a safe manner is a bit tricky. For handbrushing, a good solution is Liquitex acrylic paint mixed with liquitex acrylic medium, possibly a touch of water to thin it. To minimize brushstrokes, use a large soft bristled brush.
One option to consider, there are plastic films which may be stretched over a rigid frame and then heat-shrunk with a hairdryer to get a solid flat looking surface. In fact, small aircraft are made using this technique. Since the film shrinks around the frame, the frame needs to be really strong. Steel wire and high strength solder if properly designed should do it. The PVC pipe should also be ok, I would think. If interested in this technique, tapplastics.com might even have some pre-tinted plastic sheets that would work for this purpose and suit your needs at not that painful of a price. They're pretty good people to talk to in my experience. They help you order the right thing to do your project.