What I do for all skills is use the online skill calculator to calculate what level my current skill is in proportion to the level of (say) my BLM.
http://www.ausystem.org/~aushacho/gbox/ff/skill-e.html
For instance, I'm 222 Staff Skill. At 75, I have a cap of 240. But I'm not worried about the cap really. I'm worried about what's going to give me skill ups.
I do some modifications on my level in the calculator and find out that at 70 I cap at 222. (Actually, I cap at 223 at 70) so I need to fight monsters that are level 70 and above to get the skill ups I want. 70 Monsters will carry me to 223. 71 -> 226, and so on, and so forth.
I then take my target level (70 or above) and compare it to a listing of available monsters that are level 70 and above. I normally reference Alla.
The other day Stouter and I were farming eyes in Den of Rancor. Milloneyes are level 73-76 so they were giving me skill ups. A few moments later we went to SSG and hunted Mindgazers. These monsters are 66-72. Unfortunately, we were only fighting the really easy ones and I got no skill ups because they were all below level 70.
A bit long winded, but that's how I operate in terms of skilling up.
For elemental magic, I did that in PT's. But I'm also a BLM so it comes a bit more naturally to me than RDM. Enfeebling however, I am not 100% capped (though close) and I go put a lone Steelshell asleep in the Tree.