Although I agree with other posters that weight may be an issue (the bird may be "hot"); leaving that aside and focusing upon manning for the sake of discussion, I resolve these issues with new birds very early in the process. If this is a manning issue (tameness) then it is less about food association, more about aggression. Untame birds use aggression to thwart/control stimuli they don't trust. Conversely, You need to thwart/control their aggression as you work to build their trust.

Regarding footing the bare hand, you need to control their foot movement by holding the jesses. This should be one of the first things you accomplish in manning the bird - typically, I resolve this issue long before I start jumping to the fist (in the first few days). You can ease up on the jesses as the bird becomes trustworthy with its feet while you touch and inspect them.

Some birds are initially "bitey" during manning - the process where I acclimate the bird to being handled on the glove, having its feet touched and examined, having its keel evaluated, and touching its beak/cere.

The problem is that the birds quickly learn the value of this behavior (you stop bothering them) and so they repeat it. Some folks (bless their heart) advocate just sucking it up - but lets get hurts. Some folks advocate holding a hard object (small stone or key) and manipulating it so the bird bites down on that item - uncomfortable for the bird, so it deters. Unfortunately, birds are usually smart enough to differentiate between the object and your flesh.

If I encounter such a bird, I round off their beak tips. A bird with a round-coped beak will bite down, twist and pull the skin on the back of your hand for all it's worth - to no effect. So they stop. It may look less elegant for a little while, but they sharpen up again in a few weeks. In the meantime you have the added benefit of the fact that it is more difficult for them to break into prey items (squirrels in particular). This helps teach them not to bump away when you make in. After the bird realizes that it needs you to open the kill for them to be rewarded, they settle in quickly to your reward/trade-off routine.

One way to skin the cat.