First, here is a video I made for spinal cord dissection:
If you can’t access this, send me a PM.
You want to move as fast as you can. So do the opposite. Take spinal cord first, then DRG. You need to remove the SC to access the DRG anyway, right?
I use spring vannas scisors to cut the lumbar cord into 4 quarters. If you want to take just dorsal, cut it in half axially (like slicing a sub sandwich long ways). This takes some finnesse, but it works. If you want to be more precise, you’d need to use a Vibratome, but that is much more involved and probably won’t change much.
Keep everything clean. I use RNase-free PBS to moisten the cord so the scissors don’t stick.
Have cold tubes ready to snap freeze your tissue in (dry ice).
For processing, there are a number of kits. I like the Direct-zol from Zymo or the Qiagen RNeasy kit.
You can take the DRGs after if you want, but if you want SC, prioritize that and get to it as fast as you can. No more than 5 minutes to freezing. You can perfuse with cold PBS, oxygenated PBS if you want to try to buy you some time, but that’s more work.