Ah, yes . . . senior moment! However, same principal applies to photographic paper. Why not produce your postcards on postcard-size bromids, NOT RC paper, and use an inkjet or laser printer to superimpose the postal bit on the back? You can't use RC paper for this, ink or laser powder won't stick, so rather limited to stock that preferably doesn't have the maker's imprint on the reverse - that leaves out Big Yellow. Perhaps a Kentmere FB paper? I used to do this many moons ago, but have to admit one advantage of digital printing is that it's a helluva lot easier to produce postcards, greetings cards and the like! I would add that I'm a 'hybrid' - wet work as well as digital.