CB isn't really setup for ideal bulk emailing to begin with. It'd probably easier to put people into appropriate AcyMailing newsletter subscriptions and just fire off a newsletter as needed. This is significantly more efficient if the criteria doesn't change. Until we've a way to save filters (you sort of can using URL structure) and have mailer templates no matter what sending bulk emails is going to be a pain.
If the filters don't change and you need a way to filter the user manager down rather quickly and repeatedly it is possible to do this with URLs. It's kind of a pain to format, but the below explains the structure.
Parameter: usersbrowser[filter_advanced][0][column]
Value: Field ID
Parameter: usersbrowser[filter_advanced][0][operator]
Value: URL Encoded Operator (see below list)
Equal to = %3D
Not equal to = %3C%3E%7C%7CISNULL
Less than = %3C
Less than or equal to = %3C%3D
Greater than = %3E
Greater than or equal to = %3E%3D
Contains = LIKE
Does not contain = NOT%20LIKE%7C%7CISNULL
Is one of (,-separated values) = IN
Is not one of (,-separated values) = NOT%20IN%7C%7CISNULL
Parameter: usersbrowser[filter_advanced][0][value]
Value: URL Encoded Value
Notice the [0]. That's the repeat usage row. This means if you supply all 3 parameters you'll have 1 filter row pre-setup. If you supply a second set of parameters, but change [0] to [1] you'll have 2 filters pre-applied. Example as follows.
&usersbrowser[filter_advanced][0][column]=46&usersbrowser[filter_advanced][0][operator]=%3D&usersbrowser[filter_advanced][0][value]=test
That reads as "First Name - Equal To - test" as the field id of 46 is the first name field. You'd just add the above to the end of your user management URL. If you construct such URLs for common filters you can bookmark them and quickly get back to that filter list.
That's the best I can suggest for now to maybe help with the issue.