This is how the chinese restaraunts (a lot of them anyway) get all there meat to taste the way it does.. make a mix of bicarb soda and water and marinate anything in it... it destroys the protein in the meat and makes it taste that weird, super tender way. It is also the cause of a belly ache you get sometimes form chinese places if it hasnt been washed off properly.
For my bet, if ya need to do this you have deffo bought a cut worthy of a stew not a BBQ. its expensive to buy good quality stuff and if you go to a butcher.. get the organic grain fed aged stuff... scotch fillet i think ranks as number two behind fillet steak for tenderness and it should never be chewy unless ya boil it....
sear it in a hot pan or bbq and let it rest for at least 2 minutes and thats it...