All sounds good stuff to me...
I used a jetwasher on my huge Oly trailer, and the
old paint came off in sheets. If you can get a steam
cleaner, then that'd probably do it even better.

Following all the advice listed here, I'd be tempted
to try the jetwashing first-that'll get the loose stuff
off first, then nitromors or similar on the more stubborn
bits.

The advice about catching all the sh1t on a sheet is
a good advice, otherwise you could end up in serious
poo with the environmental laddies. Don't use the nitromors
with the trailer standing on your lawn, or on your
neighbours driveway either!

The most important thing once you've got the old stuff
off, is to get a good coat of etching primer on the
bare metal. Etching primer combines(don't ask me how!-no
doubt some spod will write and tell you exactly..)
with the Ally and forms a solid base for the top coats.

Have fun!