Low sodium beef broth is a good base. I usually use apple juice to add a bit of flavor along with a touch of salt (not much, after all, you started with low sodium broth!) and a touch of sugar. The worchesteshire is a good additive along with a bit of rub, garlic, etc. I don't use these flavors in my injections, but that's just me.
I use a brine injector (ball pump with a hose) and a 10" canula with about 8 holes so getting the injection into the meat is NOT a problem. With a Cabela's type injector you cound use herbs and such and not deal with clogging.
Use your imagination and add or change one thing at a time until you find "your" injections. DrBBQ's is a great one to start with.
Southern Brethren BBQ Competition Team
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KingFisher Gator Rotisserie cooker, WSM, Stainless 5 burner with IR gas grill, Turkey Fryer, Weber JD Commemorative grill, slightly used Bandera chamber for future use as a cold smoker, Masterbuilt 40" insulated ELECTRIC smoker