When preparing for a smelly foot client, I wear the same pair of trainer socks to the gym for as many days as I can (even just one day will do, but the more the better), and leave my socks tucked into my trainers the rest of the time.
Then the night before I put that pair of socks on, wrap my feet in cling film then put uggs on (obviously only around the house, its quite slippy trying to do anything more!). Sometimes sleep in the clingfilmed socks, otherwise leave them to fester in the clingfilm.
On the morning of the session I wrap my feet in cling film and plastic bag with gaffer tape around the top so I can shower everywhere else (its not always perfect, but it prevents most of the water).
Next its back on with the socks, wrap them in cling film, and either ugg boots until a few minutes before he arrives, or if I have another booking I wear them under a pair of kinky boots!
If it is just feet rather than feet and heels I just take the cling film off before he arrives giving them 10 minutes to dry off a bit and let the client take off my trainer socks.
This method has never failed me, and it is less intrusive to your life than it sounds!