I grind my head into my opponent's face when I'm stuck in a tight rubber guard. My goal is to distract my opponent so that they can not analyze my defense at their leisure while I attempt find some wiggle room. Also, I intend to make them uncomfortable. I do this to Eddie and he has never complained. It wears on an opponent psychologically and encourages them to transition to a position where I will have more freedom of movement. It is hard to attack while another head is pushing down into yours.
In regards to "pains moves" as a whole, it is better to see these moves from a teammate than to learn they exist in the middle of a tournament. I do not encourage my students to use pain moves, other than the grinding their head into their opponent's face. Personally, I do not like to use things like the knuckle in the throat move but I deal with it when it happens.
On the other hand, there are times when pain is inflicted to open your opponent up. For instance, if your opponent has a great kimura defense, you can drop your elbow into their ribs and they usually let go of their defense. Or if you have mount and your partner has a great T-Rex, then you might want to push your forearm into their throat so their arms will come out so you can attack them.
Whenever I show them a pain move, I point out to my students that if they go there, their competitor will likely respond in kind; so save dick moves for when you need to punish someone for using dick moves on you. Or because you need to open your opponent up.
In regards to "pains moves" as a whole, it is better to see these moves from a teammate than to learn they exist in the middle of a tournament. I do not encourage my students to use pain moves, other than the grinding their head into their opponent's face. Personally, I do not like to use things like the knuckle in the throat move but I deal with it when it happens.
On the other hand, there are times when pain is inflicted to open your opponent up. For instance, if your opponent has a great kimura defense, you can drop your elbow into their ribs and they usually let go of their defense. Or if you have mount and your partner has a great T-Rex, then you might want to push your forearm into their throat so their arms will come out so you can attack them.
Whenever I show them a pain move, I point out to my students that if they go there, their competitor will likely respond in kind; so save dick moves for when you need to punish someone for using dick moves on you. Or because you need to open your opponent up.