I think Merlin’s guide is a good orientation coming from the DT. It has a pretty helpful thread, but the PDF is solid.
I would start with static samples only that you load from your personal collection and play with scenes and the crossfader. I found that once I wasn’t confusing myself with the live sampling capabilities, it was much easier keep track of what was going on and reigning in the chaos.
You might also feel constrained by the way patterns work on the OT, I know I was. With the digi series, every pattern is a different part meaning you can assign a different sample, filter, etc. for each pattern. On the OT you only have four parts for every bank of 16 patterns. Your kick drum can’t be changed on pattern two without affecting pattern one unless a sample lock is used (which can be painstaking) or you set up another part. It takes a while to adjust, but you can make just as varied and interesting music with four parts and being able to switch parts independently of patterns opens up some really crazy possibilities. For example, My workaround for the earlier problem I posed with kick drums is that I have a sample chain with 64 kicks on it and now I can choose between 64 kicks on any pattern.
Once you are familiar with the static machine and how parts and scenes work, then add the flex machine and the rest to start learning how to sample and modify external gear and sound sources.
Best of luck!