XrmToolkit provides the ability to modify role permissions on a per-entity basis. This makes it easy to create and modify permissions for entities.
To access the dialog, right-click on the solution node in the Visual Studio solution explorer window. Then select the 'Edit Entity Permissions' menu item found under the 'CRM' sub-menu.
Once the window is open simply select the entity from the dropdown list and the current permissions will load:
Editing the permissions can be done in a similar manner to using the CRM interface when editing permissions on a single security role. Clicking on either the column or Security Role name will update the permissions for the entire column or row.
You can modify one or several entities before saving. XrmToolkit keeps track of all the changes and will update them all at once.
Once you have edited the permissions simply press the 'Save' or 'Save and Close' buttons to update the permissions in CRM.