Well, Hopefully You CAN Teach An Old Dog A New Trick (Part 2):

Day Two and Day Three have come and gone.
           The progress was thus...

Step 4 of Day Two and Day Three: GETTING DOG TO STEP ONTO STEPS.
           This went well.
           Bingo was induced to place both front feet on the top step to reach his treat.
           Cue, much rejoicing.

Step 5 of Day Two and Day Three: GETTING DOG TO REPEAT STEP 4.
           This went well also.
           Cue more rejoicing.
           Buoyed by this success, we felt emboldened to try to progress to Step 6...

Step 6 of Day Two and Day Three: GETTING DOG TO GO ALL THE WAY UP THE STEPS.
           Thus far, abject failure.
           Bingo will place both front paws on the top step with encouragement, but that's it. Once in place, the back of the sofa is close enough - or he is long/tall enough; whichever - for him reach the treat by stretching.

So! Tomorrow, we shall try holding the treat on the top of the sofa's backrest, so that it is in sight but out of reach.

Early days.
           We shall persevere.
           And in our perseverance, we shall prevail.

B.C.B.F.L.B x