I'm pretty sure that if you polled dahlia lovers, my method would definitely be in the minority, but it works for me. For starters, I'm a more informal garden type of person, so mine are interspersed with other plants in some places, and grown like an informal hedge in other parts of the garden, so that might have some effect on the aesthetic value of my method. Also, I am not trying to grow my dahlias for show.
I use a single bamboo stake.
I don't take off any stems.
The stake gets put as close as possible to the sturdiest stem and is tied to it. When there are many stems, I loosely tie one big loop around the entire plant and stake. Generally, I only need one loop, about 1/2 way up the stems (I don't put the loop on until it seems that the plant will get floppy). The main stem might get tied on every couple feet.
The fact that my dahlias are interspersed with other sturdy plants and/or grown close together as a hedge helps the plants be supported.
I wish I had a picture of my dahlias last year.

I use pretty much the same method as mytime. The bamboo stakes are the biggest I can get around here, about 7 ft. tall, 1" in diameter. Mine are all planted together in a massive bed (massive for my yard - 35 tubers) Last year I did get a summer storm with high winds that blew several of them over. I lost a few branches, but not a complete plant. I am thinking about doing more pruning this year, and keeping them at one stem per plant (some had 3-4 last year). From everything I read, I will have less blooms, but bigger ones and stronger plants.

Dig the hole, pound in the stake and then plant the tuber. I use 5 foot lengths of 5/8 " pvc pipe. It comes in ten foot lengths and have the hardware cut it in half. If you buy the grey; rated outdoors, it will last for years and years. Tying starts when the plant is one foot tall, again at about 2 feet tall and then whenever it needs it.
BTW, skinner pvc, while cheaper, is waaay too amusing when you are trying to pound it in, it arcs and wangs around.

Disbudding and de-branching will get you better stems and larger blooms.

Rebar makes good stakes and at Home Depot they will cut it to length. Also,. steel t-posts are great, 6 foot ones are about right. I believe that if you have room, dahlias do best tied to stakes. Four dahlias planted around each stake and the stakes need to be 5 to 6 feet apart. This is the way they did it in the 1920s and later. They get lots of sun and you can walk all around the plants. Most commercial growers have gone to planting in rows. It just does not look as good.

I go with re-bar. 5 ft lengths driven home well. I only plant one tuber per stake but a friend grows two per stake. I tried the upside down tomato cages but seemed to get in the way when working around each plant. I paint mine a dark green rustoleum. May try the gray PVC. Sounds interesting and would certainly be lighter than rebar. Steve in Baltimore County.