if you have the OGs and MG guides, that should be enough. it's really about practice, documenting which problems you get consistently wrong, and making sure you figure out exactly why you missed them. if you do get through all the problems (which takes a while), go back and the ones you missed and see if you missed them again.
if you want to diagnose weaknesses, take a real practice exam from GMAT. that will probably give you the most accurate representation of your strengths and weaknesses.
also, here's my debrief which goes over more stuff in detail.
8-t66345GL