When i get home i'll explain more in depth how the coolant flush machines work, for home purposes you are better off using a diff method...
1. add coolant flush additive
2. idle car for 10-15 minutes
3. after cooling, drain coolant
4. close petcock on radiator and insert water hose into mouth of rad.
5. fill till full, start car, open petcock and let run for about 5 minutes keeping an eye on the temp gauge, never let it get above normal operating temp
6. shut off car and let water drain completely
7. close petcock and fill with favorite coolant, cooling system sealant, and cooling system conditioner.
the main advantage to coolant flush machines at shops and why they charge so much isnt so much the machine as most shops use BG additives in which you have to be a technician or shop owner to purchase, the cans dont even come with instructions, if you havent been trained to use it you arent supposed to be using it.