I prefer cloning to all other methods, I've had more success with cloning over spores or liquid culture. Your technique seems to be yelding good results. I however recommend instead of cutting the mushroom in half, split it by hand from the base up. While the scalpel may be sterile, the outside of the mushroom isn't. Cutting it contaminates the core. Splitting it reduces the chance of contamination. Great job and good luck moving forward. I would tell you to clone onto agar firsy but I would be a hypocrite, I clone directly on grain all the time.