I shower before I go on a trip, right before.
Usually try not to book itineraries with long layovers.
I think last year, I was at CDG for a couple of hours layover and reached the AF lounge for a business class award.
I did see the bathrooms there but I had showered before boarding this intra European flight so really no need.
Now if I was going to India or something with a long layover in HKG or maybe somewhere in the Middle East, I'd look into something like that.