To add a little more info, the original 2nd generation iPod touch (MB model) does not need SHSH blobs yes. I've successfully downgraded mine from 4.2.1 to 3.1.2/3 a few times for older app compatibility.
The 2nd revision of the 2g iPod touch (MC model, 8GB only) has a newer bootrom shared with the 3rd generation and it does need SHSH I believe. They may have found a way around it by now but not that I know of off the top of my head.
Shouldn't be too hard to grab the IPSW, put it in DFU mode and restore with iTunes, but you might need to install an older version or do it offline, not sure how iTunes 12 handles it. But it can be done.
MB model, was on 4.2.1, downgraded to 3.1.3.