Sorry but I had to quote you here. The reason is because the anti-jump cue crowd always LOVES to say that a jump cue makes it so that ANYONE can jump in two minutes and that the cue does all the work.
If it's any consolation Yu Ram Cha can't jump either with a jump cue either
Well what I mean is that I watched her dog several fairly standard jump shots because she was set up incorrectly for the shot. Yu Ram actually does jump well but on this day she was not setting up right and not following through.
The answer to your question is no. Clean balls make no difference whatsoever.
The two things that make all the difference are a chalked tip and your technique. Assuming that your jump cue is made to the standard of jump cues over the past 15 years which is ultra hard tip and light weight, 9-7oz at least.
What you want to do is stroke through the ball like you are going to drill right through the table. Focus on making your tip go past the cueball and through the table. YOU WILL NOT HIT THE TABLE!!!!!
REPEAT - YOU WILL NOT HIT THE TABLE.
But you have to stroke as if you will. Otherwise you are pulling up short and losing all the energy and that's why the ball won't jump.
You know how it is when you short stroke a shot and you know as soon as you hit it that you pulled up? That's what is happening when you are a halfway decent player but you can't jump.
Now you do need to make sure you are hitting the ball in the center or close to it. A lot of people line up right and then they lunge forward or drop their shoulder and this causes the tip to go too far up or too far down and changes the angle.
No matter what jump shot you have you need to make sure that your cue tip is splitting the cueball in half so that you know you are at the center. THEN you can adjust a little up or down depending on what spin you want.
The clock face is the same just as it is with a normal shot - you just need to make sure that your cue tip is dead center of the clock no matter what angle. If you do that then you can easily switch angles and find the one that is right for the shot.
How do you find the angle?
Simple, take another object ball and hold it on top of the ball you want to clear. Now mentally draw a line BACK through the center of the top ball to the cue ball. That angle will be the minimum clearance angle you need to get over the ball with a normal stroke.
Now you can cheat by hitting the cue ball much harder and use a lower angle - the harder hit will make the cue ball go higher. But this is something that you will learn with time and get a feel for. The reason you would use speed or force over a medium stroke would be to shorten or lengthen the path of the cue ball - such as jumping a long distance into a small area.
If none of this advice helps you then I suggest you go buy the latest magic jump cue because as everyone always says it's the cue and not the player when it comes to jump cues - don't you agree?