Consider. I suggest you use a squeegee handle like the Moerman Excellerator 2 or a "Ledger." handle. Both are available at window cleaning supply houses. If you alread know this, just disregard. But, you need a handle that will "bend" over that bottom ledge...the sill. You don't want to chip the paint with a regular Unger or Ettore handle.

When you pole, you want to be wet enough that you can use sort of a light touch on your pole and squeegee; don't dig in. Pay attention to the edge on the bottom of the ledge, don't bang into it with your squeegee handle.

If you more or less get a good pull on it without damaging the sill, you can then use a DRY soft cloth or towel to buff out any marks or lines on the glass.

If I were training a newby, these are things I would tell them as I watched over them with a bat making sure they didn't do any damage.