Normally I don't like to necro a thread. But I have a question along the same lines. I'm playing obscurity and I need a tall mushroom farm. The problem is this pack doesn't contain MFR and the progressive automation farms don't work. Axe of the stream doesn't work so setting up a TC golem farm is out. So I'm wondering if anyone else has a good suggestion.
If you've got EnderIO, its farming station may be able to do it; I'm not sure. If you've got Agricraft, then it should almost certainly work on mushrooms growing on Agricraft crop sticks.
Failing that, if you don't absolutely need the giant mushrooms, you could set up a vanilla-style farm for small mushrooms, using water streams, pistons, or mod-added block breakers to harvest the ones that grow.
If you do need giant mushrooms (if they give extra drops in Obscurity, if the small mushrooms are just too slow and/or would need a farm bigger than you want to deal with in order to get enough of them, or if you just like overengineering stuff in ridiculous ways), then you'd need a block placer to place small mushrooms, a fake player (such as an Autonomous Activator) to apply fertilizer, and some way to harvest them. The last is likely the most difficult, but is possible with the right mods and some engineering. I don't know what mods are in Obscurity, but if you've got Funky Locomotion or a similar mod and some block breakers that don't mind being moved (AE2 annihilation planes work well), you can set up a frame contraption to handle it. If you've got RFTools, its Builder block has a mode that should be able to do the job. For that matter, with Botania, you could even pull it off with a wall of mana spreaders with bore lenses, some redstone, and a bunch of cleverly-placed mana pools.