Press radial button, then just move the mouse in the direction of the action you want to do. Have "get in", "get out" always in the same place, so you can access them rapidly and without having to look at all the available actions. So instead of having to scroll the mouse, read the different actions possible, then scroll to it, and then press space, you open the radial menu, then you have a quick look at every action available, maybe add some icons for faster recognition. Then move the mouse at the action you want to do and release the radial menu key.