"it depends" For example I was able to get a duna encounter just by eye-balling both angles, but I've heard that Jool takes more precision (haven't been there myself yet - been busy working on a different project) The ejection velocity is how fast you have to go, as it reads out on the nav ball. In reality this ejection velocity isn't important. It would be the exact speed you'd have to reach if you could apply an instantaneous "burst" of thrust up to that speed, but since rockets accelerate smoothly, the actual speed you're going when you see the encounter pop will be somewhat different. Another tip is to start your burn somewhat before the ejection angle. Since, once again, the rocket doesn't immediately get up to speed you need to give yourself some time to accelerate.