In response to your questions about "being on well water not always being able to keep up with the watering regimen."
Here are some suggestions.
1. First and foremost- mow the lawn at a high setting. Mow no shorter than 3 inches. You could go to 3 1/2 to 4 inches even. First of all, the longer grass blades will create more "shade" on the soil surface and reduce evaporation of any moisture that is there. Secondly, the depth of grass roots are proportional to the the length of the blades, so the longer the grass blades, the deep the roots will be. Soil moisture is always greater deeper in the soil.
2. If you do any watering, do it when it is least likely to evaporate. Thus early morning is the best time. At noon on a sunny day, some of the water will evaporate before it has a chance to percolate into the soil.
There are some treatments that work best with water - for instance, nematodes to reduce grubs. After a treatment such as this, water the most important parts of the lawn first. You may say, if I can keep the front lawn protected, that is more important than the back lawn that fewer people will see.
3. Increase the water capacity of the soil. Sandy soils are very poor at retaining water. Clay soils will retain moisture to a point, but once they get dry they are hard to accept moisture. In either case, the best is to add more organic matter. Organic matter will increase the water holding capacity of sandy soils, and will help to break up clay soils so that the water will become more available to the lawn. Organic matter is best added after a core aeration, so that the organic matter has a better chance of getting into the soil profile. Organic matter sources can include black soil, peat moss, composted manure, as well as other mixtures that have been formulated for lawns.
We do have dry compost that is spreadable with fertilizer spreaders.
4. Sometimes the best way to use water is to wash the car. That always seems to bring rain soon after.