I'm new at having geckos, but while at the vet the other day he did panacur my leo. He just put drops on his nose and she licked it off. Hope this helps.
I am currently treating one of my leos with Panacur. The vet gave it to me in a little syringe and it seems to have been watered down. I just squeeze a drop on on to my geckos nose and she licks it off. I would recommend making it in somewhat of a watered down paste so that it would be easier to administer. Make sure you get the dosage correct as well.
You need to be able to administer the proper dosage! The paste form of Panacur is formulated for horses, not a 50 gram gecko. Also, unless a diagnosis for specific parasitic infections has been made, there is no reason to give you gecko Panacur.
If you insist on giving Panacur to you gecko, the proper dose is 25-50 mg per kg of body weight. You will also need to determine what the concentration is of the paste to accurately calculate the dose:
Dose (25-50 mg) X weight (50 grams= .05 kg) divided by the concentration.