cabosil is silica powder and is used to thicken resin to give it a property so it won't sag when you are doing a vertical layup. It's my guess that is why other resins are blended thick to make them more user friendly. Mix micropheres to resin only after the resin and hardener have been blended together to a dry micro putty for a light weight filler. I found that using this system, the filler spread easier and sanded easier, the drier you got it the easier it was to sand. I've used thicker resins and found that MGS was more user friendly and not as toxic
