No you want a fair amount of leaf to coat with Glyphosate as it will soak into the sap and then be carried down to the root system, so the more leaf you can coat the more weedkiller will be attacking the root.
I have read they are older than the hills and are keen to live. I have found pulling up regularly is sufficient to reduce their growth and spread (I don't use chemicals on my allotment). They contain spores that will happily spread so be vigilant. NB the root is v dark brown / black.
You need to kill the root or it will just keep coming back.
Get yourself some gardening gloves and wear them to bruise the leaves (rub them between your hands to break up the waxy surface of the leaves) then rub into the leaves some resolve 24 or other weedkiller containing Glyphosate the higher Concentrate the better) You will need to keep treating but it will eventually die.
We moved house at the end of last year, now spring is here we find that our front garden is overrun with horsetails. Tried snapping them off, they keep coming back, there are 100's off them covering the flower beds, coming up through the lawn and invading the drive. Does anyone know how to get rid of them, looked on google and it said vinegar, but surely that will upset the soil pH and kill everything else?