Let me tell you that there is no such thing as a quick sketch.
OK not strictly true. Let me re-word that - there is no such thing as a quick sketch that will be useful to the client or to the designer.
ANY sketch that makes it into a client's hands is a carefully thought out exercise to make sure that it is true to what the end goal will be and will visually portray what the designer needs to communicate to improve the client's understanding.
Prior to that sketch there are many hours of thinking and 'what'if'-ing that go into making up the final components.
It is possible to cut down time spent on the sketch itself (using a less time intensive medium for example (this will be individual to each designer)) but you can not short cut on the preparation that goes into it. You can also help yourself by asking what is the most important focus of the sketch - what exactly is it that you need to communicate?
Before the weekend I managed to pop a few 'quick sketches' off to a local club who are undertaking refurbishment of their club house. I had a meeting on site a few months ago and explained my ideas to a colleague to pass along to those in charge.
The sketches I sent portray in simple form the impact the refurbishment would have, and that is the important thing here.
I therefore used bold strokes in terms of colour. It is not a scaled accurate sketch at this stage but a taster to pique interest in the possibilities: