Using the cocktail, or any synthetic fluid for that matter, when you already have shifting problems is going the wrong way. It has been stated countless times that if your syncros are questionable you should try running a dino ATF+3 (or +4) to see if it helps the situation.
If it does then that's a telltale sign your syncros are going bad. (VERY common on pre-revised MTX-75s & still not perfect on revised
)
If you have no notable change then it can be a different issue.
The cable adjustment issue has come up many times and there is a good how-to on shifter cable adjustment.
Sometimes it's even a result of worn out cable ends that just need replacement.
