What additive can I add to Jelly Wax/Gel Wax to increase its cooling time/setting time?
At your own risk, you can try using plasticizers for waxes. Usually, these plasticizers are wax esters of palmitic acid (well-known example is spermaceti, which can be replaced with jojoba oil, or you can buy/obtain those esters). But it's hard to predict exact amount of plasticizer needed. Add too much - and it will be creamy I-will-never-cool substance. I hope we have chemical engineers here who know more about wax plasticizers and can add details to my superficial statement.