I purchased the Gardiner System (electric pump spray) to clean a high level interior, each pane was approximately 18' x 7', it worked but I found it difficult to control the spray i.e. often too much resulting in multiple pad changes. I would suggest you try the Vikan Head & Pad System or suitable equivalent on a suitable pole, spray the pad with pure or your chosen cleaner (Nilglass works well) and clean away.
Darren (Smudger) has posted on this topic, might be worth a search.