Are you able to be more specific about these "lumps"? There are a couple of products that you are able to spray for earthworms, but I do not think they are labeled for earthworms. I have had luck spraying yucca extract and watering it in. They make a product called Early Bird which is a granule and you can apply it with a fertilizer spreader and water it in, but it is not very cheap. Early Bird is not cost effective in my opinion. Most texts will say deep and infrequent is the best way to water, but I think that may change. Light and frequent watering can achieve deep dense roots as well.
If your grass is lumpy, I would recommend aerifying it. I don't know what kind of grass you have, but I would recommend "power raking" too. Verticutting (power raking) is actually better at removing organic matter and thatch than aerification. Aerification is more beneficial at adding oxygen into the rootzone.