
I think the only other way you'll be able to learn support/healing Blue Magic will be to confuse an enemy, and I believe the only way you can do that with your party is to equip someone with a Dancing Dagger (which you can't get until the Moogle Forest), hope that it casts Tempting Tango, and then hope that the enemy in question casts the right spell on the right party member.

I decided to try to take on the Gil Turtle, because I'm a masochist idiot BRAVE HERO.
What an awful fight. For starters, Zeninage does a whopping 0 damage, so if you were hoping (as I was) that the fight was easily cheesable by a Samurai, you're wrong. Its physical attacks remove about 2/3 of my characters max HP, and it counters every attack with a special move that deals damage similar to its regular attack while also inflicting a slew of status effects (and it hits two of your party members each time).
The strategy I ended up using was to equip my party with evasion-boosting items like Elven Mantles and to move them all to the back row. I would cast Golem to protect my party against the Gil Turtle's attacks, and I would damage it exclusively by using Hi Potions on it, which hurt it since it's undead (and no, Elixirs and Phoenix Downs do not allow you to cheese the fight either). Since it would counter every Hi Potion with it's one-two special on top of its regular attacks, I would have to recast Golem frequently (my stony buddy could take 4-5 hits per cast). And every now and then the boss would get a hit through, leaving me scrambling to try and heal up my now poisoned/paralyzed/blinded/aged party member(s). (!Animals was useful thanks to Nightingale healing both HP and status effects, but it only had about a 2/5 chance of coming up.) And since Hi Potions only dealt 500 damage per use out of the GIl Turtle's 32,768 HP, combine that with all the healing, summoning, defending, and MP restoration I had to do... well, I had a long **** fight ahead of me.

BUT I **** DID IT

...and then everyone died because Quake dealt over 3000 damage apiece, and I had no Blue Mage, Time Mage or Chemist to cast Float on my party.
BUT IT STILL COUNTS IN MY BOOK! BONUS BOSS SWAG POINTS WOOOOOOOOO, OMEGA AND SHINRYU HERE I COME
PARTY WIPE COUNT: 13

Carbuncle had some strong attacks, but was slow enough that I had plenty of time to heal. I mainly relied on physical attacks to damage it (!Rapid Fire was very useful since it got around Carbuncle's high evasion), and the fight was over pretty quickly.
I get the feeling Carbuncle is going to be a very useful summon, considering I have no White Magic to complicate having Reflect on everyone.

Gilg was a pushover. The only issue was trying to keep everyone free of status ailments.

Golem and Carbuncle were crucial here, though I had to recast them frequently. Most of the damage I was doing came from physical attacks, with the odd summon here and there. The first time I fought him, he wiped out my entire party with a single cast of Lv. 3 Flare, so I spent a little time grinding everyone to a safe level before trying again. Once I did that, it ended up being a fairly easy fight.
PARTY WIPE COUNT: 14
Onto the final third of the game...
Four Job Fiesta Summary
Kat - 1. Thief 2. Summoner 3. Bard 4. ???
Val - 1. Thief 2. Summoner 3. Ranger 4. Samurai
ML - 1. Blue Mage 2. Summoner 3. Ninja 4. Samurai
RU - 1. ??? 2. ??? 3. ??? 4. ???
Squeege - 1. Monk 2. Mystic Knight 3. Ninja 4. Chemist