One parameter of this method is the 'AccessControlList'. Create a new 'AccessControlList' and fill the 'CustomComponent' property. Initiating the CustomComponent is not very easy, but you need to go through that.
If I understood correctly, Shoeb has asked if it is possible to make specific properties read-only dynamically (before document is created). I think your proposal is referring more on setting permissions on the whole document and not on specific properties of that document object.
The best solution I know is to use metadata card rules to control which properties should get read-only on which workflow state. This works well. We have used it very often to hide, show and make properties read-only after specific workflow state.
