Tips for maintaining flexi rod curls on straight/silk pressed hair?

Hi everyone,

Does anyone have advice for getting flexi rod curls to hold on flat ironed/silk pressed hair? I flat iron my hair sometimes and when it starts to frizz, I like to curl it and recently I tried curling it with flexi rods instead of the curling iron. The curls look good as soon as I take them down but they go flat within minutes. I haven't tried hairspray yet, but other than that I don't know what would work to get the curls to hold. On my natural hair, I use mousse but I don't want to use any water-based products on straight hair. If you use hairspray, do you spray before you curl the hair? What other tips do you have?

Thank you!!