No knack to the anchovies as far as I’m aware.
Thread/squeeze the anchovy it onto the tool, jab it into the hole (enlarge hole with knurled spike tool if necessary). Pull tool back out, use sharp blade to trim so there is about 5mm sticking out of the tyre, re-inflate tyre and you’re good to go.
I bought the kit I linked above to get the tools then when I’d used up the strings I got about 50 on ebay for a fiver. They were a bit too thick so I used a sharp knife to split them down to size, this also means that I have a range of sizes for different sized holes.
The fact you can fix the puncture without even removing your wheel or tyre is a massive win in my opinion.