It's not quite as effective as xanthan gum but I find arrowroot flour works wonders. You can also try locust bean gum or psyllium husk (soak it in water before mixing so that it can dissolve)
Those are more starchey than the gums and are meant to be mixed with amaranth, rice, quinoa, or other more coarse flours it gives you that same "slimey" start that hold the bubbles as the bread cooks. That's generally gone by the time it's cooked.
When you're using guar gum, try to keep the quantity down to about 1% by weight of the dry ingredients. Also give it time to fully hydrate before adding the rest of the ingredients. I normally mix mine in dry with the flour and then add milk or water to get things wet and then leave it for a couple minutes before continuing.
If the gum (or even the arrowroot flour) is properly hydrated it will be more effective in baking. Plus you can use less liquid overall which is good because it's easy to overdo the liquid in GF bread.