Gessoing bargain boards

I found on bargain on oil painting boards and I was so excited that I bought about 50. They are still a good bargain but the oil paint doesn't adhere properly. They are pre-gessoed by the manufacturer but I had to gesso them, again, to make it work. After I finished the previous little oil painting, I spent an hour gessoing the bargain boards. My kitchen counter and all other available horizontal surfaces have gesso boards drying all over the place.
I will sand them tomorrow and gesso them with another coat.