what is the combo you're trying to do?
you can just TK a stand alone HCL.
I find that the problem most people have isn't the actual 6FRC6 part but the simple fact that they're not jump installing properly.
If you're using her auto-jump install tricks (tech-fall/hoverdash) you need to be aware that they require you to be almost 100% on point with your inputs.
If you're using stand alone jump installs then you should be doing the negative edge method.
If you're JI'ing via mixup make sure that you're pressing c.S/K before you actually press 8. An easy one to learn for this is Note, 66 JH/JK,JS then 2K, S89632H14(789)6K 6FRC6
Another trick is to gattling c.S into K, it gives you a huge window to input the JI.
As for queues, you just have to learn it. It'll take ALOT of time so don't get discouraged if you can't get it right away. (kind of the main reason no one plays I-No)