SoFoBow for silver (good ol' 6 SoFos)
That can be very misleading. Even though that is the path you took, by posting it here, it implies that you would recommend that path to this person. Seeing as SoFos aren't anymore, a Rainbow wouldn't be good for farming FGs efficiently.
Hopefully I'm not off topic, but for silver I used the Bone Collector with great results. I also used Chaos Wyrms but was surprisingly less effective than the Collector. And yeah, cause shards now have their own element a SoFoBow is not a good deck for farming silver.
The parenthesis were more of a warning
SNBows are still quite fun to farm silver though (AD101 and Wrecking Ball use no shards and are still effective), you'll still be getting shards/rares and getting electrum (which is laughable in bronze). PSNbows are also really good (plus there is a tutorial for building them somewhere in the forums).