Oral dewormer for wtf

[Crispy42]

So in the latest installment of "sick frog from Petco" Steve has now had a positive fecal test. The vet found nematode eggs in his fecal sample. She prescribed fenbendazole as an oral liquid, but little Stevie isn't being particularly helpful in taking the meds. I have to give him one dose now and another in two weeks, but for that I need to get him to open his mouth!

Since he's still so tiny and my credit cards seemed awfully thick I used a plastic shirt collar stay instead. I was able to get his mouth open once, but without a second person helping I couldn't get the syringe in his mouth before he closed it. Other than cursing my lack of a third hand, what can I do to get these meds in my stubborn little guy who doesn't want to open his mouth?

Steve is about 1.5" long and is already in a quarantine tank. His diet staple is crickets, with occasional dubias (when he will eat them) and waxworms and butterworms the past few days (since his appetite has been a bit low and I needed him to eat so I could get a fecal sample!)