How to use Views to send a Mailing to a Selection of Recipients?
I'm assuming what you have is a bunch of Drupal users that you are segmenting using Drupal field values.

Step 1 Go here civicrm/admin/synchUser?reset=1 and make sure all your Drupal users are in CiviCRM.

Step 2. Create a custom field for an individual. Make it Yes/No. Call it My Group or whatever. Make it searchable.

Step 3. Make sure that you have the custom field group added to the database config in settings.php /civicrm/admin/setting/uf?reset=1 so you can use it in Drupal Views.

Step 4. Create a view of CiviCRM contacts. Use a Drupal UID relationship so you can filter them into the group you want. Add the custom field you created in Step 2 to the view. Add a VBO filed. Modify the Entity value of the custom field. Bulk edit the custom field and set it to 1.

Step 5. Go to CiviCRM and search for contacts with the custom field set to yes. Add them to a new Mailing Group.

So you could have this as a smart group. You users just have to use VBO to add in the custom field value to update the smart group.