Keeping your manual flying skills up by regularly using them is the easiest way. If you need to do it in a non-normal situation and haven't done it in the last few years it's a bit late to start training it. Of course flying manually to 15000 and back down is not very challenging for those that do it, it is however very challenging to those that don't. Especially in IMC. And it trains basic skills which one might need in a bad situation and frees mental capacity to deal with other stuff.
Legally you can get away without any real manual flying in the simulator event every 6 months. It is legal (at least in europe) to do the OEI pattern on autopilot, the required non precision approach on autopilot and so on. Passing SIM checks doesn't mean anything as the legal requirements are way out of date. SIM checks are there to tick boxes, not to check skills. Which is one of the major problems right now and has ultimately lead to the current mess.