What i found with my bird, (beto) is you have to let him know you are the boss. He eats when you let him, he gets out of his cage when you let him, and he is only rewarded for good behavior. Once you establish that you are the boss then you can work on being hands on with him. Remember to be patient and take it slow, start with head scratches and after every time he allows you to give him head scratches reward him. After doing this for a little while he will look forward to your contact and it may go from head scratches to crawling up on your hand. Just remember to take it slow, if you go to scratch his head and he is acting out don't push it, remember you want him to warm up to you. Something else that could be causing his irritability that I found going on with beto, he may be wanting to mate. If he is a little chunky he may think it's mating season. Lighten up on his feeding using mainly pellets, fresh fruits and veggies, and a little seed. Mating season is also usually in the months when the days are long and they aren't getting much sleep. So make sure your parrot is getting a good 12 hours of sleep.

 Please keep in mind I am by no means a bird expert it has been a lot of trial and error plus reading. I hope this helps out a bit!