Definitely get with the team leaders of the places you want to cross train in. I have been known to do small bits of training at a time for sbux, fitting room, etc. . . . Basically, grab the TM for 15 or 20 minutes every time we are scheduled at the same time and start with the basics. Before long, you are halfway trained and it just makes sense to the store to complete your training. Ask your HRTM to print learning plans for areas you are interested in. You may already know how to do some of it. Offer to cover breaks too. That's another way to sneak in some extra cross training. If you aren't scheduled 8 hours, offer to come in for an hour before your shift starts to get some training. I know hours are tight, but just one hour might be ok. (I would point out any call ins as a way to justify it). Also, I know a couple of instances where a team member took a shift from the swap board that he wasn't trained for. Ended up getting approved and the TM got trained for it. In that case, it was an area similar to the TMs original area. (Cashier took SD shift, HL took electronics shift).
Team Leaders all want good, motivated Team Members. I have current baristas who were cross trained in sneaky small doses. Before anyone realized it, I had them on my schedule. One of the ETLs has told me to keep away from her teams, lol.