Liking the woodwork, Simon!
A few words on polyester and epoxy resins as finishes on wood:
Polyester (what most people call "fiberglass") resin has poor adhesion on wood, it also eventually yellows and becomes opaque if not protected from sunlight with a UV resistant varnish. There are "water clear" casting resins, but they aren't designed as thin finishes -- they are for casting. I'm sure it can be used where sunlight isn't strong for some interior purposes, but i wouldn't put it on a banjo.
Polyester laminating resins do not cure on the surface in the presence of air -- they are designed that way so the next layer of glass fiber roving or mat or cloth, whatever the schedule is, will adhere to the last one in the mold. The next layer of resin and catalyst will kick it hard, though will also have a sticky surface to accept the next layer.
The final layer of resin is called "finishing resin" and it does have wax added, as Andrew said, to block air, and allow a hard surface cure on the inside of the molded item. Finishing resin can be bought that way -- you don't have to add wax -- it's pre-waxed. It's no good for laminating of course, because the wax prevents further adhesion.
Epoxies also yellow and go milky opaque very quickly on exposure to sunlight-- even more quickly than polyesters. They are a poor choice for something that is finished bright where you want to see the wood.
Talc added to lacquer makes a fine sanding sealer under paint, however it isn't very clear or even and isn't good under a bright finish.
Here's what I would try for filling the meranti grain -- spread a very small amount of carpenter glue on a small patch of the surface, and then immediately, before it dries, sand with fine sandpaper. This mixes fine sawdust with the glue and wipes it into the grain divots, while removing it from the surface. The color will fit well, just slightly darker in the grain than the meranti, as it should be, but a good tonal match.
This also works well with small cracks in glue joints. There a trick to sanding enough, but not too much to fill what you want, and to sanding in the right direction to fill, and not pull out your filler material. But a little practice on scrap will show you what to do.
Hope that helps!