Question about mtn biking with flat pedals. If you have a decent set of flat pedals (real pedals with spikes not the plastic things that come with the bike), do you also need a dedicated shoe or can you get decent pedal hold with regular running shoes?

I've always ridden clipless but I've read enough times that riding with flat pedals, even occasionally, can be good practice for pedaling technique. I might be willing to buy a set of pedals to experiment, but not if I also have to buy yet another pair of shoes that are uncomfortable until I break them in.