If there's a very girly option when buying any ordinary everyday thing for him, either buy it for him or insist that he buys it… For example, make sure his shaving gel is pink, or he has girly pink shampoo and soaps, or a pink toothbrush, etc. The general rule, is if its available in a feminine or girly format, that's you make him have.
The idea here is to get him as many gentle small reminders possible that he will see constantly in his everyday life, so that he sees you are openly recognizing him as a sissy, and more importantly, you are reinforcing him being a sissy through this humiliation. It's this subtle, but forced recognition and affirmation that he is a sissy that will bring him delightful embarrassing erotic stimulation.
If you are in a shop buying something at the same time, remind him that he's required to buy the more feminine option. Tell him if he weren't such a sissy you would let choose whatever he wants, but as a sissy girl, he can only buy products for girls. If you are shopping on his behalf, just choose the most girly option for him, and when you give it to him, remind him that you got the most girly option, just for him.
You should do this anytime you are buying anything together, or anytime you are buying something on his behalf.
If you are in a store, you may want to point out that the girly products are for him, so that other women can see him humiliated.
Don't let him talk you out of buying the pink or girly option….insist on it. It also needs to be your initiative. Remind him at the time when you are buying…don't wait to see if he'll ask.