A friend of mine tried 'Bark' he only does gutter cleaning and clearing.
He says, for him, it's not very good:
The customers on there are looking for the cheapest price, so will get loads of quotes.
You have to try to contact the customer before anyone else does, and that could be a minute from getting the lead.
It's quite expensive for what you get.
He told me that for window cleaning it would be a definite no, that is however, just his experience.
Personally I like leaflets, a simple design with a picture of you and your van and list out everything you offer in an easy to read list. Nice big telephone number at the bottom and keep it friendly.
Don't deliver them yourself, have a look around and see if you can find someone to deliver for you. I got lucky and found a guy who would deliver 1,000 for £30 in areas of my choice. He also sent me a tracker photo so I could see where he'd been. He did deliver mine with about 3 or 4 other leaflets but I still had a hit rate of 4 customers per 1000. Some areas you'd get nothing, other areas you'd get more but the average was about what I mentioned.
As has already been said, you need to try different ways of advertising, find out what works for you, and your area, and then stick with it. It's trial and error.