I do it on plants im growing outside, I justy either mound the soil up around the stem or place an old plant pot ive removed the base from and fill with damp soil, I only try it on one plant first (generaly), but if the stems don't look like their having moisture related problems I go right ahead and do it to all of them.
I must admit that ive never done it so high that I go up to any lower side branching.
The other thing I find better then doing this method, is cutting the base out of the pots im growing in, (just enough to create a lip around an inch wide from the side of the pot base) Then I place a few disks of pollystyrene raw meat food container dishes from the supermarket frest meat counter so that I can remove them and place the pots directly onto another pot of fresh homemade compost with pearlite added for aeration.
This works better then mounding up soil around the main stem and adds to flower production greatly. Wish I had the pix to show you, but alas they were all on OVERGROW R.I.P (miss u tokahontas)
I grow in pots so I have the option of moveing them inside a polly tunnel if frost or weather is a problem. f***ing UK weather. although I once had 30 original DP white widow plants @ about 5ft + tall and one morning they were covered in snow from the night b4, didn't harm them at all, but had to chop early as I had over pruned them far too heavily and as a result stunted their natural growth/flowering to much to let them continue & bud rot eventualy signaled time to chop and cut my losses.
Give it a try if you can, even a shallowish tray used to catch excess water filled with soil can help roots grow out of the holes in search of extra goodness can make quite a differance. Rudi