It's not necessary to gradually fill in the soil. It may speed up growth as the tuber is exposed to the sun and its heat, but definitely not necessary. Many people just plant the tubers at the appropriate depth and cover with soil.

so....squirrels won't mess with the tubers before they start sprouting?

Also, I still can't decided what to support them with, an inverted tomato cage or stakes. I want them to look neat and tidy since they will be seen from the road. I keep reading that these things grow like tomato plants, tomato plants I've grown in the past look a lot botter in cages than grown next to stakes. Any thoughts? thanks

I can't recall every reading anything about squirrels disturbing the tubers and I really don't think they will especially if they are planted in. They very well may come by and have a snack on the new growth though. Perhaps someone with more knowledge on the subject will have a comment.
I will be planting over 50 plants so I will be using the 5 foot metal stakes covered with green plastic that I purchased at "amleo.com". They look decent (as decent as a stake can) and I was able to get them for about $1.65 per stake, including shipping. I may use a few tomato cages in the areas where "Big Foot" my wonder dog has difficulty minding his manners.

I was worried about squirrels when I should have been worried about cats, got home yesterday, found where the neighbors cat used one of the holes for a bathroom. Tuber was exposed but didn't look hurt.

Rinse off that tuber if a cat peed on it! I wish I were kidding. I lost numerous tubers last year due to my cat using the holes as a litter box before I figured out what was making them rot. I think the urine is really high in something bad for tubers...can't remember what though.