I’ll also raise my hands saying I never used the ‘look at the end of the runway’ advise. I’m not a trainer so I don’t pretend to know how to teach landings, but one things for sure: often enough there is no end of the runway for you to see. So what do you do then? I look at the blocks and the surrounding periphery.
As pilot monitoring I use a side glance at the runway edge to asses how long an inadvertent float is gonna take and wether I should take over or not. I find it much easier to judge the closure rate that way, or the lack thereof.