You start variegated brug cuttings the same as any other brugs. Snowbank seems more difficult to root but that might just be me. I haven't had a problem rooting any of the other variegated varieties. If you only have a few cuttings to start I'd go with soil. I use water when I have a large number to root but I think soil gives you better results. Good luck.

Cuttings of firm new growth taken June through Sept. apply 0.1 to 0.3% IBA Rooting hotmone stick in well drained soil & mist taking 20-80 days to root & 1 year to form a 1 gal pot.

There is NO soil (or shouldn't be any) in a container potting soil. That's why they also call it a soil-less mix. What exactly is a soil test going to tell you about a potting mix? That it has no nutrients or none to speak of is about it!! The 5-1-1 mix has virtually NO nutrient load at all and the vast majority of other potting soils do not either unless added by the manufacturer. Or containing materials that are not advised for a container soil like real "dirt" or compost. I've been growing plants long term in containers for more than 30 years, mostly trees and shrubs, and have undertaken a lot of research into container soils and fertilization, both for my own purposes and for the classes I teach. The best container soils are heavily textured and aerated and with minimal decomposable organics that can alter fast drainage. All required nutrients are supplied by the grower, not the media.

i've tried it once with begonia cuttings, when i had to be away for a few weeks. it's basically a passive hydro wicking. you don't need to set up a forsythe pot, you can just insert a wick on the perimeter of any pot about 1" deep and drop the other end in water container. the width of the wick and how much peat is in your mix will determine how much it will wick. the clay pot and/or twisted acrylic yarn will wick just a little. i use the top wick method all the time with succulents to keep them going without bother of watering (i have a lot of plants and i am away a lot too).