Wind and Fire Blast Technique
Advantages
1.) I get the power of 2 jutsu and only consume the chakra from one
2.) Very wide scale attack
3.) Area based, so precision isn't necessary
Disadvantages
1.) Only long range
2.) I need a clone/ally
3.) It takes the time of two techniques, so it is fairly slow
Counter
I would counter this technique by extinguishing the starting flame from Intense Pain. If that is put out before it hits the ground, it will never erupt. If it doesn't erupt, Pressure Damage has nothing to intensify, and becomes its own sort of threat instead of becoming one much worse.
Utilization
As generic as this is going to sound, I would use this technique when I find myself using a clone. I don't make clones typically, and I am not the type to make one solely for a technique. So if I need one for something else, I will probably use this technique while I can, just for its sheer force and size.
Performance
Trunks stand next to Sasuke Uchiha, a friend from the Rain Village, and prepares for their dual assault against a clone. Trunks quickly weaves a series of three hand seals while Sasuke forms the ram hand seal. Trunks then spits out a small flame towards the ground around the clone, which erupts into a hell storm of flames. Simultaneously as he does this, Sasuke releases a blast of wind that levels everything along its path before entering the area of the flames. Once it contacts the other technique, it greatly increases the size and intensity of the heat it puts out. This would happen mere meters away from the clone, roasting him in an instant.
Advantages
1.) One hand seal
2.) Almost too large to avoid
3.) Can be used at any range
Disadvantages
1.) Very slow
2.) The power is spread over the technique, so due to its large size, mere contact wouldn't be very damaging
3.) Because of its size, it makes me lose sight of my opponent
Counter
The only way that I can see countering something like this would be to lower the ground that I am standing on to the point that the fire passes over me. This is because it is too big to completely extinguish, and dodging really isn't an option either, because fire would be everywhere that I would think to go. Going underground is risky, but it will protect me from the flames.
Utilization
I think I would use this technique while my opponent is landing from a jump or another technique. This is because very few people can use the flight technique, meaning that they can't stay suspended forever. Once they come to the ground, fire will be there waiting for them.
Performance
Trunks forms one hand seal and concentrates his katon chakra. He amasses a great load of this chakra before using nature manipulation to convert it into a ginormous wall of flames, which slowly spreads over the battlefield. It would be enormous in stature, and would cover almost the entire battle ground. After a few moments, your clone is completely engulfed by the flames.