Chapter 4 Tower
In the first mission of the "tower" there are 2 priests at the top/center of the map with psychic rods (the strong ranged healing rods, I can never recall the spelling of those things), kill everything but those two. Beforehand, of course, equip your new 2 dragons with the half-power transformation and experience doubler skills. The half-power transformation will decrease their damage to the extent that they barely damage anything, including the priests, but yet still get a large amount of experience per attack. Also, put each dragon the square below the priests, you don't want them to get any bonuses from each other (dragon auras). For some time, the priests equipment will fully heal their wounds after each round. AS SOON AS you start causing more damage than their equipment auto-heals, skip attacking them that turn (that they don't have full HP) to lengthen the "leveling" process.
Also abusing the battle-saves (IMHO it's a must-do since dragons have SLOOOOW stat gains) I managed to get this process going long enough that I managed to nearly max out the prince and our old friend to the point that, with the "blessing" and the permanent-battle item transformation, our prince was a level 35-ish black dragon that was toe-to-toe in stats with his father (excluding his HP bonus obviously!). Needless to say it made the last stages of the game *considerably* easier. :)
I admit it's cheap, technically just a hole in the system (I wonder if they put it there intentionally?) but it can be a big help if you're having trouble in the final tower. :)