... To help your baby deal with the fast flow of milk, position him so that his head is slightly above breast level.
With a younger baby, the football hold works well in this situation. Sit so that you are leaning backwards slightly, such as you would while sitting in a recliner. This enables gravity to help slow things down.
You may want to try lying down on your back and allowing baby to perch upon your chest as if he were nursing uphill or climbing up your chest.
You also may either pump or hand express until the flow of milk slows down and then put your baby to the breast or you may wait until letdown occurs and then take your baby off the breast while at the same time catching the milk in a towel or diaper. Once the flow slows, you can put your baby back to the breast. In time, with maturity, your baby will learn to deal with the fast flow of milk with more ease and will probably prefer it!