If there is a stubborn pattern of karma or hang-up that you want to remove from your soul using ansuz or munka would be your best bet. Karma can be tied to curses from the enemy or also from other negative patterns in past lives, aside from the fact that the enemy curses Gentiles in general. Combining the aforementioned with cleaning and RTR's is the best way to go.
There doesn't exists a formula to know when you are cursed.
You should be very advanced in perceiving yourself and the energy, to detect that someone is sending you a curse.
Regarding MUNKA, it is usually used to clean the soul and remove bad karma and blockages. I won't add more since Shadowcat already gave enough information on that.