How to set and access local parameters when launching a nodelet?

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I know how to set and read local a parameter using a plain node with

"_param:=value"

on the command line and

string value;
ros::param::get("~param", value)

To get the value in the code. But all my attempts to do so with a nodelet fail.

I need to add a local parameter to a nodelet I start. I though I need to add it to the my_argv parameter:

nodelet::M_string remappings;
nodelet::V_string my_argv;
my_argv.push_back("_param:=foo");
manager.load("NodeletName", "my_namespace/NodeletClassName", remappings, my_argv);

And in the nodelet, after onInit() in some callback I have:

std::string param;
ros::param::get("~param", param);
std::cout << "param = " << param << "." << std::endl;

Which prints param = .. I also tried getPrivateNodeHandle().getParam("param", param) with no success.

I guess I'm doing it completely wrong?

The background is, that I want to start load multiple nodelets of the same type but with different configurations. Perhaps there is some other canonical way for that?