Keeping it simple and safe.
I know I use 3 things before opening my mouth to say positive rate and it all occurs in a couple of seconds.
SENSE: if I can hear T/O thrust and I can see the attitude passing through 12* I know that we are probably airborne.
and
INDICATION: check IVSI
and
CUE: my peripheral vision confirms for me the ground is getting further away.
”POSITIVE RATE”