Re: easily accessible videos of Internal Training in Aikido?
A tangible lexicon for Internal Training, particularly for Western students, is only very recent, as in the past 10 years or so, largely thanks to a very small handful of individuals who have labored to create a comprehensive and transmittable language that is directly connected to physical training.
Earlier than the past decade, you had to go to Chinese systems, tai chi in particular, to get terminology that related to actual physical concepts and training methods that produce internal skills. And even then, if a teacher was not forthcoming in explaining and teaching what each of those terms represented, students came away with only partial or completely incorrect understanding.
The sayings and written teachings themselves are usually deeply couched in poetic, metaphoric language that is impossible to decipher without a guide who is willing to do so. Hence, all of the misunderstandings that have arisen from the doka and other sources of wisdom whose meanings have remained, until recently, largely hidden.