I strongly recommend things like walking on a bench at the park or on a wall alongside you in your neighborhood... (prep for plank and seesaw)... also get a "collapsible leaf bag" from home depot - it's tarp material and has a spring that holds it round, and which expands when it is not collapsed, so that it stands up - like a barrel... CUT the bottom out with scissors and Voila! You have a mini tunnel. Wedge it (between chair and couch, or wall) or outside put a tent stake through one of the toggles that hold it in it collapsed position - the goal is so it does NOT roll...and gently encourage your dog through it.. NEVER "push" a dog onto or through anything.. but put some biscuit in it, throw a favorite toy through it (and block the run-around options).. soon you will have a tunnelaholic!
When it's raining and my guys don't want to go out in the yard, I send them out to the tunnel which I leave out there!
Also if you have a coffee table or chair without cross bars, you can drape a poncho or light tarp/drop cloth is better (tarp is too heavy) over it and again work your dog into it as a "closed tunnel" or "Chute" practice!
keep us posted on your progress...