Curious to know about how much paint(basecoat) would i need to do the entire car correctly?

 

are you using Testor's rattle can?

i suggest you talk/email these guys:
www.paintscratch.com
www.paintworldinc.com

 

It'll prolly take about a 3 qts to gallon to cover the whole car. I have never painted a whole Fit before but that would be my estimate. With the new waterbase basecoat, you should pick a proper undercoat to get more hiding. Unless, you are repainting the whole car with the same or similar color you wouldn't need undercoats.