Reginald Scot says that the ointment "whereby they ride in the aire" was made of the flesh of unbaptized children, and gives a recipe. He also gives a recipe using bat blood. I recommend you try the bat-blood one first.
Here are the two recipes, as reported by Reginald Scot in 1584; he does not claim to have made these ointments himself, but he has them from reputable sources.
Take: "The fat of yoong children, and seeth it with water in a brasen vessell, reseruing the thickest of that which remaineth boiled in the bottome, which they laie up and keepe, untill occasion serueth to use it. They put hereunto Eleoselinum, Aconitum, Frondes populeas, and Soote."
Or; "Sium, acarum vulgare, pentaphyllon, the blood of a flitter mouse, solanum somniferum, and oleum. They stampe all these togither, and then they rubbe all parts of their bodys exceedinglie, till they looke red, and be verie hot, so as the pores may be opened, and their flesh soluble and loose. They ioine herewithall either fat, or oil in steed thereof, that the force of the ointment maie the rather pearse inwardly, and so be more effectuall. By this means in a moonlight night they seeme to be carried in the aire."