When I met my now wife (blind), I had never even seen a tandem in real life. Our second date was to try out a rented tandem in Central Park. She didn't have tons of tandem experience but did have some. I, as mentioned, had absolutely none. We did at least two full laps (6 mi/lap) on the main loop and might have done more but the brakes on the Fuji Absolute (otherwise a perfectly good bike) were extremely worn down. The actual mounting and riding I had Googled (Proper Method) and my first posts ever, to BF, were in the Tandem Forum. It's kind of overthinking it, I think, to imagine that riding twogether requires any more than doing just that. A trainer will insulate Captain and Stoker alike from the very forces that are important to experience and get used to. Pedaling is the least of it. I call 'Stopping' (stopping pedaling, not necessarily coming to a stop) as a courtesy. Since we ride linked through the timing chain, I could simply stop pedaling and that would be that. I never announce the resumption of pedaling and it has never been an issue. So, this was just a preface to the TL;DR which is: I hope that trainer and/or the means of adapting it to tandem use is cheap, because it won't be money well spent.