Yeah I kept a few items to swap onto slaves when it was training time: Maid Dress for +1 Spirit and +1 Loyalty, Lacy Underwear for another +1 Spirit and Leather Collar for +2 Loyalty. Definitely helped get the points for Break and Date.
Since the advice regarding using Dates for most of the Loyalty gain, past the first 2 unlocks at least, I've had few issues keeping their Spirit up. I really only have problems if the training type(s) needed for the specialty I'd like have started off at Resist. I was pretty happy when I found out that you can switch trainers though, it's allowed me to swap in a caster trainer to use Mind Read a time or two to figure out some of their Dispositions before hitting proper training.
One question I still have though is the Spirit Status that displays once their training is complete. So far I've seen it say "Preserved" and "Retained" I'm assuming one is for training completed at high Spirit and the other is for closer to the 50% point, there's no tool tip or info to suggest there's any functional difference between the two. I've yet to complete screw up the training yet so I can only guess there's at least a third type, "Broken" would be my guess, but it'd be nice to get some confirmation on whether there is a difference between the first two.