Spraying lubricant onto a dirty chain is worse than doing nothing. Here is the sequence we use in the bay.
Almost every chain that arrives here is wearing a black paste, and that paste is the problem rather than the protection. It is old lubricant with a season of grit held in it, sitting exactly where the rollers turn.
The sequence is not complicated and it is always the same. Degreaser on, left for a minute to work rather than wiped straight off. A brush on all four faces, meaning the two sides, the top and the underside, which is the face nobody does and the one that carries the load. A rinse, low pressure and never at the seals. A dry, properly, with the wheel turned by hand and a rag.
Then the lubricant, put on while the chain is still warm from being turned, onto the inside face so that centrifugal force carries it out through the rollers rather than flinging it off the outside onto your wheel. A minute for it to creep in, then the excess wiped off. A chain should look faintly wet, not black and dripping.
Two things people get wrong at home. They spray the lubricant on cold and thick, so it sits on the plates where it does nothing and collects dust. And they do it after a wash without drying the chain first, which traps the water in.
On this island, once a month is the right interval for a bike ridden daily, and after any ride that has gone through standing salt water it wants doing that evening rather than next week. Salt water on a warm chain overnight does more damage than a month of dust.
If you want to see whether yours needs it, put the bike on the stand and turn the wheel while looking at the underside of the chain run. If the rollers are black and the plates are dry, it is due.