Wd40 is all I use for cleaning and lubing chains. If you use one bike and bike 300 miles or less a week, you just clean and lube when you wash your bike at the end of the week. If you have 4 or 5 bikes that you rotate then maybe once every three or four weeks. If on the other hand you only ride 100 miles or less a week you can use wd40 as a cleaner/lubricant every 3 to 4 weeks.
If you have removed manufacturers lube with paint thinner , mineral spirits etc, wd40 will not be enough. You'll have to resort to one of the methods mentioned here. Other wise wd40 works to both clean and lube when manufacturers lube hasn't been removed. .
Tip, using a rag as a back stop, simply spray chain as you turn cranks slowly making sure to wipe at the same time.