When having an Asado or generally with other grilling methods, you can bring flavor to the meat in three different ways.
- Classic (most people know): apply salt, pepper, other spices, spice blends before grilling, optionally a little oil, and then onto the grill.
- As is often done with Asado: for example, while grilling, sprinkle the meat with a Salmoera, that is, a brine with various spices, to not only add flavor but also a bit of moisture to the meat.
- Season very little or not at all beforehand and only add a little salt afterwards, then for example add a Chimichurri, a Salsa Criolla, or another sauce to bring in flavor.
So there isn't just one way, but what tastes good to you. What you like best. That is the right thing. Just try it out. Something new, and then it will be good.