Ah righto. I only really fry chicken schnitzels and chips. In the chase of schnitzels, I usually just grab a couple of crumbs from the bottom of the bag (I buy mine predone from a butcher) and chuck them in. Most of the time I do just eyeball though. If it’s smoking, the oils too hot, if it’s sizzling and crackling I evidently didn’t dry the pan right, and it’s probably a bad idea to put it in right now (I’d rather chuck it in when it’s a little too cold than have it spray me in the face)