First I gave him around 10 days/2 feedings to relax and feel less stressed out. Then every day for 5 days or so I picked him up and did it for about 2 minutes and put him back in his cage. By the 6th day he didn't show any signs of aggression toward me whatsoever. If you own a ball python you will eventually get bit, even the nicest ones will sometimes strike at you. You just need to reach in an grab him, don't show any fear, his bark is worse than his bite trust me.
Edit: It is important to give him time before trying this, or even attempting to handle him period. Snakes aren't cats or dogs, they don't like to be held or stroked. While most tolerate it, it is still stressful for them.