Figs are fairly easy. Blueberries are tough. Some cuttings will not root or leaf out if not in 100% humidity. Misting systems are used for those types where the cuttings are sprayed every 5 minutes to every hour depending on type.
You can make your own misting system, with pvc, misting heads, and timers. Giving high humidity to fig cuttings helps a lot. I just put them in potting soil. I re-cut end, dip in rooting hormone and put a gallon plastic bag over them. Once they leaf out I wean them off the high humidty, cutting the corners of the bag, then the top is cut off, and soon removed. I keep them indirect bright light.
Here's one I'm doing. I never heard of using a heating mat. I do not. If you're getting mold, the cutting is probably dead. Cut away all mody parts, the rest of cutting might be ok. Perlite will not hold any water, it is added to mixes for good drainage of water, it adds air space too. It holds zero water. If you used DE like this it would work since it holds 120% of it's weight in water. Vermiculite also holds water.
