I put about 2 tablespoon of vinegar in the softener dispenser part of my top loading machine then add about 1 level tablespoon (sometimes a bit less) of bicarb as the machine is filling up (soon after I add the OMO). You can also buy bicarb soda in bulk quantities which keeps costs down.

This OMO product wouldn't be suitable for toploaders I don't think although I'm not 100% certain. I know that there is a thread about how the vinegar part is more important for front loaders to reduce the smell that is common with that type of machine.