I would say yes. Anything can be wand if you want it to be. I remember using a large feather as a wand before. Do not let other people say no to what you can or can not do with your practice. This is your craft. Do want you want to do . :)
A wand is a magical tool that is an extension of self and used to aid in directing energy towards a specific goal. It's a focusing tool but if the wand is say made of a specific crystal you can use the energy of that crystal to aid spells that that energy can support.
The wand, as it has already been said, is just a tool. What makes the magic or spell work is not what the wand is made of, but whether the spell caster knows what they are doing. So the simple answer is that, yes, a resin wand will work. But whether or not it works doesn't mean whether it is made out of resin, wood, metal, crystal or anything else. It all depends on how much you, as the caster, knows about doing magic.
Incorporate something into the resin wand, like crystal chips/beads, shells, dried flowers, or colors. I even printed certain symbols in PNG format on translucent paper to add them into my resin projects. Skies the limit almost with resin. I have made athames using resin and sold them. Others have made them and sold them through Etsy. I haven't heard anything about them not working. Only thing you can do is try it out. Remember though that sometimes resin can get hot while curing and that might change the properties of certain crystals, like the color. I dont think you'll need to put in a metal rod as resin is fairly strong, unless it's Copper or whatever then go for it.
If you're wanting a different shape to your resin wand you can make one from oven baked clay and cast that in a silicone mold.
-Resin, being a polymer plastic, is not conductive. ... Mind you neither is wood. However where they differ is that wood is more easily associated with correspondences and energies. It is more relevantly symbolic. So in that regard resin can be more difficult to work with symbolically as it doesn't represent anything.
But, Treat ot AS nothing, Ie empty space, and it becomes easier to work with as it can be seen as a vessel. A container of things that would instead be your actual focus of associations. Perhaps place a lightly coiled copper or silver wire along the length to represent direction and flow of energy. (For bonus points maybe use two wires lightly twisted to represent a double-helix)
-Resin (two-part Resin, at least) shrinks as it cures, creating pressure on whatever is inside it. Most Quartz/silicone-based crystals are piezoelectric; meaning that pressure creates electrical charge/energy. So those types of crystals can be viewed as 'activated' or 'charged' by enshrouding them in Resin.
-Two-part Resin also cures through an exothermic chemical reaction. Meaning it generates heat. So soft/vulnerable items like flower petals will get 'cooked', wilted, and browned. On the flipside it also means that your Resin might (if anything) be able to be associated with elements of fire. ... 'the fire within', 'effecting of change', and 'tempering through fire into something stronger' come to mind off the top of my head.
