I have the testo dual port I won off this site yrs ago, one of my favorite tools.
Before then I had a Dwyer oil filled incline manometer and u-tube manometer. The Mark II I had was about $30 and I used it to meas ESP when doing install startups to check airflow.
I've also used dt to set airflow when had elec htrs in unit.
w/o either elec ht or static chart, fall back on the pitot tube I keep on van. also have a phototach that I've used on commercial stuff. on res w/driecrt drive, the rpm=motor speed, so and oem esp chart just uses esp and motor speed tap on chart.
since comm stuff has lots of belt drive, they use blower rpm. bit of scotchbrite and esp and can use cfm chart.
questions asked, answers received, ignorance abated