advice on single-toon boosting

I 5box, and my RAF runs out in 1 week. I will have ended up boosting/gifting 3 (maybe 4) teams of 4 to 60. Because my pally on Account A is doing the boosting, the toon on that account to go with each team gets left behind.

I would like to boost up the toon left behind to catch up with the rest of its team. What's the best way to do that? I was thinking a combination of questing and mob-tagging (all un-grouped), but I heard tagging is questionable or has been nerfed. More instance boosting is an option, but with no RAF the levelling would be gruesome. Any ideas?