(Futon: Reppuu Bakufuu no Jutsu) - Wind Release: Gale Blast Technique
How you would perform the technique in battle
Looking at the opponent in mid-range, I start by gathering the wind chakra into my mouth via my lungs while manipulating it in my mouth in such a way that if I spit it out, it will create a strong gust of wind. With the wind present in my mouth, I perform 2 hand seals in rapid succession and opens my mouth and blows the wind towards the opponent making him fly back a bit from mid-range.
How you will use the technique offensively
It is better to be used offensively while in short-range as they opponent wouldn't expect a weak wind attack. But this wind pushing back an opponent can open him to many attacks like immediately breathing out fire or using a powerful lightning attack. Also this jutsu would help to disable B-Rank lightning. Also, to think in the other way like that of combinations. Since wind contains oxygen and it is the very ingredient of the very sustenance of the fire, it would be used this jutsu immediately after a fire jutsu as this would help in boosting the power of the fire by rank which in turn would make it deadly and devastating. Also after throwing some weapons, this jutsu could used to increase their speed cause them to be powerful as the increased speed would mean the wound would be much deeper than usual.
How you can defend against the tech
An D-Rank Fire jutsu would be able to calm the wind down as the fire is more powerful than the wind in the elemental cycle. Sometimes, making yourself boost up into the air or using an earth pillar on the way of the wind could help.
Whether or not you find the technique useful or interesting
The only interesting part is it's ability to blow away the opponent or power up a fire jutsu to make it even more powerful.
(Futon: Ressenpū) - Wind Release: Violent Whirlwind
How you would perform the technique in battle
Looking at the opponent throwing out two kunai towards me, I immediately react to it by focusing my wind chakra into my mouth from my lungs. Then, I open my mouth and releases the wind from my mouth while manipulating it into a stream towards the kunais. When the wind and the kunais collided, the kunais suddenly lost control of itself and fell down onto the ground.
How you will use the technique offensively
Just as you pointed out in your description, this can be better used to boost the speed of the fire or possible projectiles. Also, if any debris remains from any previously used jutsus and they are flying around. Blowing them towards the opponent would be the best thing to do.
How you can defend against the tech
Just as you pointed out, a D-Rank blast or stream of fire can possibly block this jutsu. Even a low D-Rank earth or the exact same jutsu can be used to counter this jutsu.
Whether or not you find the technique useful or interesting
Yes, I do find this technique interesting. Boosting the speed of projectiles or fire is the best part in this jutsu.