Oh yeh I know what you mean.... even though the porcelains were worth the extra dollar... they are a pain to keep up nice and shiny.
I don't use anything fancy. Im using a mop bought from woolies. They are $39 and it has a spray bottle that clips onto the handle and the spay gun is where the handles are. So you spray as you go. The mop cloth is also detachable n washable too. I put warm water with a cap of kitchen/tiles cleaning spray. I will check the name of the bottle for you.
Sweep the areas first.. Mop.. sweep again.. mop again where needed.. ive mop these tiles twice this week now... its doing my head in too...!
Ive heard some ppl use metho??? Haven't tried yet!!