A lot depends on the current finish, then how and what it was densified with. Then what If anything it was sealed with?
Normally a PSRP Pink pH Neutral Cleaner for daily maintenance, with an occasional application of stone soap would suffice. Then a Stage 3 or 4 Elica Pad if you get any stubborn marks.
However, all this is dependant on as above, how it was finished in the first place! Is the finish, Cream, Salt & Pepper or Full Exposure?