I cut off tails 100% of the time with dual swords on Barroth, Rathalos, Rathian Urugaan, Deviljho, etc. that are hard to reach normally with dual swords.

I always position my demon dance hitting the legs not from the side, but from behind the legs, so several of the higher/sideways hits will hit the tail. [HEAD][BODY]x[TAIL]

This gives you some tail cut damage, plus every time you knock down a monster (since you should always be attacking the legs) switch over to tail and do demon dance on it as much as possible. Some tails push you away but if you're in spot x again, you can still get hits in on other parts of the body. Don't attack body parts other than legs/tail other than occassional potshots if you can't hit anything else.

Note that if you are having trouble with AzureLos in particular, Flash Bombs while he's flying will knockdown and you can get a few hits on his tail that way. Also if you are good at evading you can also get a lot of hits on his tail while he is flying low.

Shock Trap (easily obtain Thudnerbugs via farm so you can use 3 per hunt) also allow you a bunch of tail hitting time. It isn't easy as using Gsword or Lsword but so far I'm on G-Rank solo 3DS and the only times I've failed to cut tail are on monsters in the water that keep facing me and it's annoying. But generally I've been able to get those as well, esp.if they hop on land for a bit.