"other than usually being too short and having to start over or too long that I have to cut yarn."
i used to have that problem too until DUH! an idea occurred to me one day. just wrap the yarn around the needle the number of stitches you need to cast on....then add a bit for the tail and that's where you make your slipnot.
It hasn't failed me yet
fyi - did you know you can do long tail in purl as well? Once I learned that I started my hats with a k2p2 long tail cast on which matches my ribbing.