Well, Marcone has Gard employed, so his resources/contacts should get the job done. However, simply knowing where to hire a Valkyrie does not mean you will actually get one, Donnar Vadderung will still have to give his ok on this one, and that might need more than a simple skillroll. Or even getting to Vadderung would require more than a simple roll but an adventure in itself. We know nothing about how Marcone met either one of them, but I would say it took him more than a phone call, too.
As for Kincaid, I would let the player roll contacts (maybe modified by lore to see that he is looking in the right circles) to get the word out, that he is looking for him. Then I would let Kincaid find him, similar to the way he found Harry in DM (I think it was DM), neutralizing his power (supernatural or otherwise) and then discussing payment options. Or I would simply deny the player to roll, declaring that Kincaid is in a contract at the moment and can't go anywhere. And last but not least: Kincaid worked with Harry because Ivy (who he is with because of her mother) liked him, and he still charged him a lot for it. Why would he let any stranger ring him up to work for him? It is definitely not his style.
