Corn starch will work, but I would try xanthan gum- it's readily available at grocery or health food stores.
Agave is a humectant, but is added to provide hold.
If you're sensitive to glycerin, like I am, I never have an issue with agave.
2C/ Coarse/ Normal porosity/ SW Florida/ Transitioning to gray
Cleanse: CJ Daily Fix, JC Cleansing Cream, TJ Tea Tree Condish
Condish: JC Too Shea, CJ Curl Rehab (both as RO & LI)
Stylers: UFD CM, CJ PP, JC Spiralicious, Darcy's Cream Gel & Cocoa bean whip