Preparing bottles is a two stage process. Stage 1 is making sure that the bottles are clean. Easiest way to do that is to wash them as soon as they are emptied. Stage 2 is to rewash them and sanitize them. There can be many months between my first cleaning and my plan to bottle - and I assume dust and dirt may have fallen into the bottles. That the bottles are clean does not mean that they don't harbor all kinds of bacteria that when you store the wine for months (or years) in anaerobic conditions those bacteria won't flourish and spoil your wine. So, just before you are going to bottle, I would pour whatever sanitizing solution you use into these clean bottles and allow them to soak for a few minutes, pour out the solution (I use K-meta and don't dry my bottles but make sure that no more liquid drips out) and then I fill my bottles. So... wash after use. Wash and sanitize before bottling...
You never mentioned this but what about corks? IMO, it is easier to cork with a dry cork, so I don't soak my corks in sanitizing solution. What I do is - and I apologize as I do not recall who offered this suggestion on this forum but I thank whoever it was - I fill a small bowl with K-meta solution and I place a colander on top of the bowl. Into the colander which sits above the bowl I place the corks I plan to use and then I cover the colander with a plate or put the whole unit inside a plastic grocery bag. Let that stand until I am ready to cork and the sulfur dioxide will have permeated the corks and effectively sanitized them.