Lots. I will assume you work and leave the house 5 days a week. Mornings are rough but if you can do it once at least before you leave that would be good. In the evening when you come home always greet him with enthusiasm. If you have had a stressful day give yourself a little time to relax and allow the stress to dissipate but handle him 2, 3, 4 times in the evening. Always end on a happy note, and be generous with a special treat. Pine nuts work well if he is food motivated.
This coming weekend, try to clear your calendar and devote it to him and focus your attention to him. Interact with him. Talk to him, ask him questions, this is the time you can act like a complete fool and dance in front of him, sway back and forth, sing songs to him. Your purpose in life is to make him want to be with you because you are fun!!! Macaws want to be in the center of the fun, not sitting on the side lines. Donovan lived in a house with 3 children that were home schooled and can imagine there was a lot of singing so it surprised me yet did not surprise me when Donovan started singing along with me. We'll never get a label or record any records but we have FUN and that is what it is about. Remember all those childhood songs you shoved into a corner of your brain, never to be sung again? This is the time to pull them back out, dust them off and use them. It doesn't matter if you forgot some of the words, just put in anything else, it won't matter. The part that matters is the connection you are starting to work on.
I know a lot of people say to sit next to the cage and read a book but when I was to a seminar with Barbara Heidenreich she does not advocate that method because if a bird is uncomfortable with you he can't 'get away' from what he is fearing because you are sitting right there and he has no place to go. Birds do better if you interact with them from a distance. In your case, since you have had him for 4 years already, this should not apply to you but I want to put this out there.
Playing games such as peek-a-boo is something they get into and start establishing contact calls. Whistling is a great way. I can usually get Kalea to stop screaming by doing our wolf whistling or another one of our contact call we do.
The two of you might make huge changes at a time but even if they are only small steps those are important too and celebrate them and any little back steps - ignore them as there will be some of those in there too. Look at it as a long term project, not something that will be complete in a weeks time. Best to go in without a time frame in mind.
Oh, about the beak holding, you have to do that quickly so he doesn't see your hand coming in and do it from the side/top. If you bring your hand up from the bottom that would give him the opportunity to nail you with the beak.