Whenever a government department is threatened with cuts, they announce that they'll cut front-line staff and not overpaid managers or worthless paper-pushers. That's why government spending expands forever until the economy collapses.
That's not how it works at all. First almost everyone is furloughed, that is, gets unpaid holidays. DoD will furlough their 800,000 civilian employees one day a week starting April 1. So 800,000 will loose 20% of their pay! Other Departments/Agencies my furlough more or less days per week or delay until after April 1. Of course employees don't spend what they don't get and the deductions for health plans and retirement stay the same. AFAIK the furloughs can last only 22 workdays or 30 calendar days and then a RIF (reduction in force starts automatically). When furloughs will start depends on the financial state of the Federal agency. Some, such as DoD will start at the earliest time, April 1. The Forest Service (US Dept. of Agriculture) will be able to hold off until 1 May or later, for instance.
The reduction in force list is developed mostly by formula and depends on skills, seniority, military service, etc. I think that most of the lists have been (or are being compiled) but not released. An employee on the RIF list can 'bump' a an employee not on the list if the employee is qualified for the position (some other conditions, too) and then that employee can bump someone else and so on. RIFs are expensive in present but will result in savings in the future.
It should be noted: “relative to the private sector, the federal workforce is less than half the size it was back in the 1950s and 1960s”