You wax the materials end grain to slow the drying process. It doesn't prevent it. The faster the log dries the more likely it will crack. You could turn it green, making it close to the shape you want it leaving it bigger in size. Then allow it to dry and complete the turning once it's dry enough. Depending on the mosture content if you turn it green, you may or may not want to apply wax to slow the drying process.