Flushing requires special tools and chemicals. We use three different techniques and solvents depending upon the conditions we are dealing with.
Before giving advise I would need to know the condition of the system and the reason for its repair.
The 124 body evaporator is very hard to flush as it takes multiple paths. It is easy to wind up with flush left in the system; the worst of all things.
If there is no debris we would use a flushing adapter to our recycler. It uses freon to flush the oil back through a fiter into the recycler. This works for oil but not for debris. To remove debris you need violent action which this method doesn't provide.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician