One other way is to have former press and spokes persons from a government taking up positions at the braodcasters. When the current (?) spokesman of Angela Merkal left as a news presenter from the ARD (or ZDF, to lazy to loo it up...),that was regarded as a braek from customs and more or less a no-no affecting the independance of these broadcasters.
TL;DR: Political parties, and not so much the "government", use soft power to influence these briadcasters. Quite often by having certain people selected for certain jobs.