Double check and make sure all the vents are open, on top of the helmet too.On my helmet, HJC, the top air flow vents look open,yet have to be slided open.Also make sure the vent at chin area is open if you have one.Maybe you could leave the shield open just a bit to let air in to clear it,I have had fogging problems in the rain on the freeway and just left my shield open enough to stop the fogging yet keep rain off my face.
Not sure about drilling holes,yet it might help.
stay safe & enjoy the ride
Thanks for your help. I really appreaciate it. I did try to keep my visor slighly open to prevent fogs and it works but the problem is the rain getting on my face. I'm considering to try some anti fog products for my visor, There might be some products out there I can choose from.