1. Inspect and identify the stain
2. Remove excess and loose debris
3. Pre-wet any surrounding foliage that may be effected by the process.
4. Pressure clean the stain if need be. Allow to dry
5. Apply the appropriate solution. Allow to dry.
6. Re-inspect the stain to see if another solution application is needed.
7. Post wet any foliage that may be effected by the process.

During the process of removing rust stains, I also like to inspect the source of the problem. Sometimes sprinkler heads need to be adjusted to limit the overspray, or the direction of the spray pattern needs to be changed to prevent the stains from occurring. Sometimes adding a deflector cover can also prevent stains from occurring. If all of these are not the reason for the staining, the water coming out of the sprinkler system needs to be treated to prevent the spread from the source. A water conditioning reservoir may be the solution.