For subjob BST, you can almost nearly follow the same camps as you did as normal BST.
Everything else is much the same, except you don't get Leave until Level 70. Otherwise, the same rules/basics apply. With any other job subbing BST, you'll have pretty much more or less a better chance of surviving. For example, using RDM, if you mischarm, simply bind/gravity it. And try again. Likewise, for WHM, your strong stoneskin will probably make it through a few hits before it goes down, enough time for you to charm again.
For NIN, if you mischarm, simply blink tank it and try again. DNC, I'm not 100% sure, but maybe make sure you have some TP to recover.
With RDM, it's possible to sleep/bind/gravity links, buying you enough time to find another pet or charm that and go ahead EXPing.
Pet wise, because you haven't got Leave, best to charm something, fight as usual. You'll most likely win with a pet at 10%~ HP left. In this case, what you should do is go find a new pet, and put your old pet on it to attack, then run out of radar range of both pets, use heel, and let your intended next pet kill your old pet. Then charm it, and continue.
Oh, if your NIN, RDM, WHM and DNC is still Level 1-10, I suggest just soloing to 20 without the use of subjob BST. (UNLESS, it worked for you with normal BST, but I don't like how pets are so weak between levels 1-20 I prefer to just get some meds/food/regen drinks and rampage against Easy Preys and such).
Anything else you're unsure of let me know. I'm assuming here that you soloed BST to 40 without much help/assistance.
