The company that asks for eye color no longer asks for apartment number.
If you cannot remember:
Females are 5'5", Asians a little shorter
Eyes are always brown; you will notice if they are blue.
If you remember their height, look up the weight for the body type on Google.
Since you generally ask the shopper-revealing Fair Housing questions at the end, you should be able to speak their answers into you recorder or smartphone as soon as you return to your car.
Follow MF Johnston's advice and either pull over and fill out the written form immediately, or talk into the recorder and speak the answers to each question on the form. That is faster and you will be able to record more information before you forget details.