So far they have tried to blacken Talansky's image, calling him a liar and a money launderer and a criminal. While this might be a good tactic in a regular case, in Olmert's case they are just making things worse.
Imagine, they convince everyone that Talansky is a money launderer. That will not help Olmert, in fact it will hurt him. No one denies that Olmert was a friend of Talansky and took money from him. How is it going to look that the PM was friendly with and took money from a money launderer? It will only make the bribery case stronger, as a criminal does not give money for free, he asks for something in return.
Olmert's team also made a mistake in their pre-cross examination boasting. They boasted that they would destroy Talansky, peel him like an onion etc. This created very high expectations. So far, after 2 days of cross examination, they haven't done much. They have basically wasted time investigating Talansky's past. It certainly seems like Olmert and his attorneys were just blowing hot air.