Start with enforcing employment agreements. That will get a lot of people fired. Don’t replace them.
Next, don’t name anybody to head departments. Nobody in charge; no work done; go home. Use vacation time if they want pay.
Early retirement programs. Lots of ways to drain the swamp.
Most of the bureaucracy at the WH and on Capitol Hill are Civil Service employees who are entrenched practically for life. You have to be an ax murderer to get fired.