Really popular in many states of the USA, particularly Texas. Slow cooked rubbed pork is cooked "Low and slow" so that it's super tender; the test is that you can stick a fork into the flesh and twirl it and the meat fibres will wrap around the prongs of the fork.
Best results are obtained with an electronic thermometer to measure the internal temperature of the meat. Brands to look for are Polder and Taylor.
Allow around 3 hours per kg if you want to experience truly super tender meat. But the thermometer is your best guide. You can "cheat" by finishing it in the oven if you have to.