Keep It Bushy is a term that refers to the gooch (the space between your butthole and your balls/vagina) meaning it should be left to grow hairy instead of shaving it clean while doing personal grooming. The saying "Keep It Bushy, and you'll have a second pussy!" describes what it looks like if you were to lay naked on your back and spread your legs in the air and cover up your genitals leaving just your butthole and gooch exposed. If you have left your gooch to get hairy the site will resemble the pubic hair above a vagina; now appearing to being a second pussy!
Keep It Bushy, and you'll have a second pussy!