Yeah, the straight to base is quite simple and effective. Only thing I would change is drop the xylene washes and do a freeze precipitation instead of evaporation. The yield isn't quite as good at first, but if you reuse the remaining naptha, you can recover the unprecipitated dmt. Also, unless you are meticulous in separating the naptha / basified water layers, you probably want to do an ammonia wash.
Also, you want to make sure you get the pH pretty high, like 13. Get a pH meter, well worth it. I'm not quite sure of the ideal pH for STB teks but this should be pretty good.