Thanks for the answer Jennifer.
I will try to use it but it still seems that I'm forced to put the feature layer into a map control to initialize it properly (I tried to do it without and I couldn't make it), and even if it's possible to work with it outside of a map, it seems that we have to do multiple calls to the gis server for a single operation, first initialize the layer, then add or edit features (this without the server obviously), and then save the edits.
Is there anything that would allow us to simply send the features that we want to add/edit to the server?
Regards,
Evgeny
Edit: I played with the System.Net.WebClient class a little bit today, and quite easily I was able to make a request to the rest api that worked. So even without any helpers it's ok.