I don't typically cook brisket, but when I cook other large slabs of meat for london broil, I'll tenderize it by stabbing it repeatedly with a fork (evenly over the whole surface, flip, then do it again on the other side), drop it into a zip-top bag, then coat it liberally with worcestershire sauce. I'll then add a good bit of soy sauce to the bag, compress out the air, and let it sit for somewhere between an hour and a day (depending on how far in advance I have to prep it).
Something similar should work for you, although you're likely going for a low and slow cook, while I stick mine under the broiler for a few minutes.
Your other option is just to serve it with a good sauce ... or catch the drippings so that you can slice the meat and let it soak in the juices before you serve your guests.