This is one for sissies with a wife or girlfriend.
Offer your partner a weekend of pampering as a special treat. If she is suspicious of your sudden change in behaviour, tell her that she deserves it for putting up with you or that you’ve done.
Explain that you will wait hand & foot on your partner, that you will do whatever she wants, bring breakfast in bed, take her out to dinner (better have this pre-arranged!) & she is not to lift a finger all weekend. If she wants to go shopping, go willingly, carry the bags, buy something for her. Most of all, be the most attentive lover you have ever been. Remember, her pleasure is all. Yours is incidental.
Offer to bathe her, dress her, paint her toenails. She is almost certain to let you do the latter.

So, you get to paint her nails. Let her choose the colour, of course. As you work, talk positively about how much you like painted nails, how different her feet look with them, how much you’re enjoying doing it, etc. Try to sound interested and a little envious. If she doesn’t offer to do yours for you, make a joke of asking if she’d like to. She’ll either think this is a great idea or be glad you’re only joking. Either way, you haven’t lost anything.
If you do get your toenails painted, make a point of not wearing anything on your feet, so they are constantly on show. Make it clear you are happy to show off your nails. See where it leads.
Even if no crossdressing occurs, you can get your pleasure from serving your ‘Mistress’. Be sure to show your subservience. Maybe call her ‘Mistress’ if the mood is right. Bow on receiving a request (or command), or curtsy if you dare. If the mood is right, ask if she wishes to punish you for any misdemeanours.
Remember, her pleasure is all. Yours is incidental.