Reddit reviews Relimed Lubricating Jelly 3 g Packet Box of 144

While I'm sure this works fairly well might I suggest some Surgilube or if you insist on mixing your own some Thick-it or for the die-hard DIYer a 25 gallon drum of the main ingredient of both, Hypromellose.

While a little more expensive than corn starch this is likely safer to use in the vaginal canal and the offset in medical expense will likely make up for it. (Not to mention the discomfort to be had.)