This is an easy yet safe tactic to go through regular CNM 20's and 30's.( What I mean y "regular" is that it excludes special ones like the CNM20 with 3 cras, which have 20-40 hp, ut can't loose more then 1hp at the time... MNKs and NINs are the key there... )
Doing it on CNM30's is more cost/gain efficient though then on CNM20's.
Some jos, like SAM and DRG aren't really liked for CNMs, so this is an easy way to get some 'ok' money for your eastman seals.
All you need, is time to level your SMN to 30 (or 20).
Form a party of 3 SMN. NO EQUIPS NOR MEDICINES ARE REQUIRED, AT ALL !!!
A good CNM to do this is the "irds of the feather", in Pal. Mines, in Waughroom shrine. The mos here are 3 NM irds. 1 oss, and 2 minions.
When you enter, all SMNs cast shiva(or which ever avatar has mos' weak elemental). then walk ½ way to the mo, ut don't engage yet. All 3 will cast Astral Flow right now. eeing not engaged yet, it will not generate any hate. Then move in closer and 'assault' the middle ird(the ig oss). Then all 3 use "Diamond Dust". Note that all 3 SMNs have to stay close, since if they generate any hate, we don't want to ird to fly away from Shiva.
All Astral Flows will deal 486 on minions, killing them on 3rd Diamond Dust. The ig oss will only receive 425 damage, and won't die yet. ut he'll only have like 5-10% left, which all 3 shivas will finish in no time.
This should take aout 1 minute maximum, and no damage or so should e suffered y SMNs.
Most of these CNMs have rather cheap drops. ut some, like irds of the feathers, have aout 400,000+ gils in potential drops.
And tw, my SMN eing 30, I'm always willing to do it ! ^^