Getting used to you and your hands is probably the best first step. It does help letting them eat from your hands. I have never had a guinea intentionally bite unless I am taking eggs away. Talk to them in a calm voice, slow movements. Use a key word with them. I use "ginny ginny ginny" when giving treats or feeding, always a white bucket, for example. This also teaches a "call word" when you want them to come.
If they are fully confined with chickens, they may become rooster aggressive. Its normally when guinea cock mature, the 1st year after hatch. Guinea hens, roosters consider them flock mates and will mate them! Not a good idea if the guinea cock sees that! then its all over for the rooster. They start by plucking feathers off his tail, and it will just get worse. Before I had good experience with guinea comingling, My wyandotte roo was losing tail feathers rapidly. I sat and watched several hours one day, and saw for myself what was happening. I also see them highly protective of the hen they choose as a mate, and will even take on a tom turkey.
Once I started free range daily this stopped. My 6 original guinea adults have their own coop now and roost every night. They still come to the "ginny" call and a white bucket, lol. Since I free range, mine aren't "tame" but my oldest girl tolerates me picking her up. When I had a large flock of guinea dumped off at my house last year, my adults ignored them. If they approached the guinea coop, they ran them off. I was able to catch and rehome them finally.
