The preload adjusters for the rear shocks on the Enfield are pretty tame, I think you could probably turn them by hand if you were pressed to do so. You can certainly do it with pliers but these tend to strip things and chip paint over time.
I like to have the right tool for the right job. I was looking around and couldn't find much available in the States that fit a 48mm, certainly not at a low price. Most of the shock spanners available today are for the larger rear mono-shocks. I found a few smaller ones but mostly from obsure English companies or costly adjustable models. I didn't want to have to send across the pond for an inexpensive tool.
I found a solution. Remembering back to when I was a bicycle mechainc I thought about all the bottom brakcet and headset spanners we had. Surely one might fit the rear shocks. It did.
http://www.parktool.com/products/detail.asp?cat=25&item=HCW-5The Park Tools HCW-5 crank and bottom bracket wrench's single pin end fits the rear shocks perfectly and only costs about $15 US. Not sure if the other end works yet, I haven't tried it. Regardless, I'll probably cut one end off to make it smaller and easier to carry on trips.
Hope this helps.
Scott