Teach me how union finances work

There is clear choice in this election, said Hudak from Dundas on Saturday. Taxpayers can’t afford to pay big union boss salaries anymore or pay for their ad campaigns, he has said.

Does Tim Hudak not understand how union finances work, or do I not understand how union finances work?

My understanding, extrapolated from conversations with union members and observations from having worked in a unionized environment, is that union members pay union dues out of their salaries, and the expenses of operating the union (including advertising and any pay the union leaders receive for doing their union leader duties) are all funded from the union dues. My understanding is that the employer does not pay into the union (wouldn't that be a heinous conflict of interest?) So the amount of money a union spends on various things is between the union and its members.

Extrapolated to the provincial government, this means that the money union leaders get for their work as union leaders and the money unions spend on ad campaigns come out of the pockets of provincial public servants, in their role as the employees. The taxpayers, in their role as employer, aren't paying for any of it. And what the unions spend money on is between them and the public servants - the taxpayers and the government, in their capacity as employer, have no say in it or authority to change it.

Am I understanding this correctly? If not, please correct me in the comments.