The only time to use WD40 on a bike is immediately after a good wash, blow dry or dry in the sun, and hit the critical areas to displace the water only.
Then, come back with the proper lube. WD40 is not a lube, and it can cause more harm than good if you try to use it as a lube by displacing the actual lube, and collecting more dirt.
I have only heard of the chain waxing on the roadies. It gets too dirty and would need to be reapplied too often for offroad use.
My favorite chain lube is White Lightning Epic Ride. It is a good hydrid of dry/wet lube characteristics. BUT....the proper lube for YOU depends on your local conditions and riding habits. For me, the Epic Ride is the best general lube I have found.
I will generally just wipe down my chain. Probably do that every 2-3 rides, or 1 ride if particularly dusty or dirty that day, then re-apply the lube. I may also wipe it with white lightning chain cleaner, that stuff is a strong solvent and don't play around! I may get on my cassette a little here and there with a brush or a rag, but that's about it........until I eventually just take the cassette off and properly degrease it, probly about 1x per year. I only do that when I'm already taking the wheel off for some other maintenance, like a broken spoke etc. I use the Simple Green Degreaser for that.
When it comes to washing your bike, it's a catch-22. Damned if you do, Damned if you don't! So, I tend to stay on the side of less is more when it comes to cleaning. You can use baby wipes to keep the bike fairly clean and avoid the problems of spraying it down with water.
Whatever you do, don't get anything near your brake rotors unless the product is specifically rotor-safe! Most dedicated bike detergents will be fine after thorough rinsing, but any lube or similar and you just destroyed your pads/rotors! You can recover them, but it is a pain, I am the type that would usually just replace them. Regardless, I always come back to my rotors with a clean cloth and IPA to try my best to avoid contamination.
