Lynne wrote:
Well, since no one else has offered any suggestions, I will. Please note
that I am not not not a trainer.

Well I am even *more* not-not-not-a-trainer than Lynne, and in addition
am lower still than even the basest aol poster, but never mind all
that! All Hail The Google Poster as I have eaten some good dog books in
my day!

The OP says:
I have a bit of a problem: two dogs ....
Installed a doggie door ...
he KNOWS it won't hurt him...
he seems reluctant to "push" on the plastic
I'm stumped!

Dear Stumped,

Add:
2 Dogs PLUS1 Doggie Door PLUS 1 Flap that (by definition) flaps PLUS
Dog 1 going thru said Flap PLUS Dog 2 following Dog 1 going thru said
flapping Flap
EQUALS 1 Flap-in-the-face of Dog 2

And Dog 2 thinketh, "Ouch!"

For Extra Credit: Let the Flap be made of hard plastic and make Dog 1 a
balls-to-the-wall retriever.
Did you arrive at the conclusion that 8 years later Shammie, errh ah I
mean, Dog 2 will still approach Doggie Door with caution? Yes, you
are correct!! ;-)

In order to arrive at the same conclusion as Dog 2 in the Extra Credit
problem above:
Remove the flap and staple a light dish towel over the hole with just a
couple of inches hanging down. Gradually lower the amount hanging down
by restapling when Dog 2 is consistently pushing through it.

Next, go to a fabric or upholstry shop and buy a sheet of clear plastic
and cut to fit. Replace the towel with clear plastic and begin again
with it hanging down just a bit . Gradually lengthen until the plastic
covers the hole.

The most difficult stage for Dog 2 will be when he has to actually push
the plastic to get thru, but the most amusing stage for you will be the
limbo stage that immedietely preceeds that. ;-

HTH!

Susan Fraser (who has managed to be all but forgotten without actually
being gone)
and the AuH2Ok9s:
BeBop a Lu SheBop SH (playing the part of Dog 1)
Shamma Lamma Dong Dong UD MH AX AXJ (playing the part of Dog 2)
and Gris-Gris Gumbo Ya Ya OA OAJ (not even in the equation)