Cameron is seeking backing for his demands for EU reforms, which he is battling to secure before Britain's referendum on membership in the 28-nation bloc by the end of 2017.
Speaking in southern Germany, where he held talks with the Christian Social Union - sister party of Chancellor Angela Merkel's CDU - Cameron said he was "even more confident after the discussions here that these (reforms) are possible and not just good for Britain but actually good for Europe".
"Not simply because other European countries will benefit by Britain continuing to be a member of Europe, but I think it's important that (the EU) shows it has the flexibility of a network and can address concerns of an individual member rather than the rigidity of a bloc," he said.
Cameron wants the EU to cut bureaucracy and shift more powers from Brussels to member states.
He is also seeking guarantees that Britain will be protected from closer EU political integration and from economic decisions made by the 19 EU members that use the euro currency.
Those demands have so far proven relatively uncontroversial.
However, a key sticking point for several EU members is Cameron's aim to restrict benefits for EU migrants for their first four years in Britain.
Critics of the plan say the measure would harm the EU's central tenets of non-discrimination between EU citizens and freedom of movement between member states.
'Germany can help'
While Merkel is seen as generally supportive of Britain's position, she has said that "the fundamental achievements of European integration" are not up for debate, in what is a clear reference to this proposal.
The CSU however has more eurosceptic leanings than its bigger sister party, the CDU, and has signalled support for Cameron's bid to limit benefits for EU migrants.
In an article for Germany's Bild newspaper on Thursday, Cameron also reiterated his belief that the changes he is seeking "will benefit the EU too, and Germany can help deliver them."
"We want to stop people taking out from a welfare system without contributing to it first," Cameron wrote.
"Like Germany, Britain believes in the principle of free movement of workers. But that should not mean the current freedom to claim all benefits from day one and that's why I've proposed restricting this for the first four years."
Cameron is later expected to travel to Hungary for talks with Prime Minister Viktor Orban, who has come under fire from fellow EU states for his hardline stance against a record influx of refugees to Europe.
The British leader is keen to avoid a so-called "Brexit", but faces a large eurosceptic contingent within his Conservative party and growing public discontent over Britain's relationship with Brussels.
Highlighting divisions over the EU, Cameron on Tuesday said his ministers would be allowed to campaign for or against Britain's EU membership ahead of the referendum.