I'd suggest a slightly different way of approaching this.
How to earn your bird's trust so they willingly choose to perch on your finger.
When you have a new bird, test out foods that they like. Once you found out that favorite food, every day, put your hand in the cage and observe your bird's reaction to its presence. If your bird shows signs of fear, withdraw your hand slightly. This shows your bird that you are listening to the feedback they are communicating to you. Over time, as their trust in you builds, you will be able to Let your hand get closer to the bird every day as their body language shows they are comfortable with your hand. When you get close enough, push gently on its chest hold your hand steady, close enough for your bird to step on and have their favourite treat visible in your palm as their reward. One day It will put one foot on your finger. Another day they will choose to step Try to get both feet on your finger. Let the pace be dictated by your bird rather than your own expectations. Then reward your bird with its favorite treat! Do this same process multiple times a day, always observing whether it's welcome or not, until your bird can perch on your finger without the treat!