to help any industrial paint stripper to work give the existing paint a good scuff with some coarse sand paper, 36 grit etc, or at least 80 grit
then paint the stripper on thick and cover the frame.
you can even wrap it in glad wrap etc to help stop it from drying out quickly
use some scotchbrite or stainless steel scourers and rubber gloves to clean it off,
then give it a pressure clean and wipe it dry with a towel, or blow it off asap.
once you get the frame back to bare metal, and file back any dags etc, make sure you etch prime it asap
give it a couple of thin coats to stop any surface rust from forming, give it a 3rd coat if you want to use it as a primer.
it's available in grey or black, so chose what's closest to the colour you are using to top coat it.
get the Zinc Rich (think it's Dymark?)
Mitre10 have it on special atm,
197 Corio St Shepparton