Well actually an easy exercise that crosses all instruments that can be done to unglue the pinky and the rest of the fingers is doing the "Spock" but with all your fingers one at a time and in various configurations.
Put your hand flat, palm down with your fingers pointing straight out away from your body with all your fingers together touching each other including your thumb.
Start by separating your thumb from the rest of your fingers without allowing the rest of your fingers to move. Extend it out as far as it will comfortably go then just a touch further to feel a slight stretch. Your fingers will likely try to move away from pointing out directly straight. Do not allow them to do so. Do this slowly at first then build up speed. It should look kind of like those old 80's workouts women doing their leg scissor exercises.
Now do it with your index finger but keep your thumb glued to the index finger so it moves along with while again keeping the rest of your fingers perfectly straight and immobile... this will be trickier.
Then do the Spock live long and prosper move but this time keep you thumb, index and middle finger point straight and extend your ring and pinky glued together to the opposite direction.
Then do just the pinky while keeping the rest of your fingers straight and immobile.
Now take your hand and point it upwards with your palm facing your face and do that entire series of exercises again. Totally different, isn't it?
Now do it with your fingers point up but your palm facing outwards.
You can also try it like the very first set (fingers pointing straight out away from you) but have your palm facing toward the ceiling.
Once you get comfortable with those you can start mixing it up.
For example... keep your middle and ring finger point straight and extend your pinky and index/thumb simultaneously. This will be quite tricky. There are a ton of variations of this I could type up and maybe I will a little later but you get the idea. These are just simple things that can be done anywhere to unglue your fingers from each other.
You can also try doing these exercises with both hands at once which is relatively easy but then try doing two completely different exercises on each hand at the same time. Doing that helps make your mind and hands be able to work independent from each other. You can literally spend hours doing different configurations.
Hope that helps some folks. Cheers.