(Konbi Henge) - Combination Transformation
How you would perform the technique in battle: I would start by perhaps placing my hand onto my teammates shoulder and gather chakra throughout my entire body, I would then focus the gathered chakra into his body, he would then have to focus on the image of the transformation, and perform a hand seal to make the transformation happen.
How you will use the technique offensively: To be honest I wouldn't use this technique. In battle at all, it is to risky, but this technique would be good to use when fighting a large opponent like Naruto and Gamabunta did to fight Shukaku, as Gamabunta wasn't capable of taking shukaku head on due to him not able to use his fore arms and therefore him and Naruto transformed into the Kyuubi for the use of the Kyuubi's claws and arms, I personally might use this technique to transform with a large summon into a large bird so that we could utilize the strength of the summon as well as take flight if necessary.
How you can defend against the tech: One would simply have to attack the combined transformed opponent so that the combination would time out and end, much like a shadow clone would disperse when it takes a direct hit.
Whether or not you find the technique useful or interesting: Not at all that useful, but like I said above, It would be useful under certain circumstances, like using it to transform into a large bird with a large summon, giving the user the ability to fly as well as utilize the strength in battle of the large summon.
(Shinra Banshō Dōka No Jutsu) - Assimilate All Creation Technique
How you would perform the technique in battle:. I start off by placing my hand onto a nearby boulder, I then gather my chakra throughoout my entire body and focus it to my hand while also connecting my chakra with the properties of the rock, so that I could utilize its properties and transfer it into my hand and arm, the properties of the rock would then cause my hand and arm to harden much like the boulder itself.
How you will use the technique offensively: I would use this technique to perhaps harden apart of my body to put more impact and strength into my taijutsu attacks, like perhaps hardening my fist to create a more powerful punch or harden the foot for a more powerful kick etc.
How you can defend against the tech: I would use the same technique to defend against it or figure out a way to seperate my opponent from the source of the hardening.
Whether or not you find the technique useful or interesting: this is an interesting technique as it is not all that great by itself but could be used in conjunction with another technique to make the technique more worthy.
(Gyorai Shin) - Torpedo Needle
How you would perform the technique in battle: I would first use a distracting freeform move like throw a explosive tagged kunai into the air above the opponent so that he would be forced to place his attention on the kunai approaching in the air, then I take that moment to gather the nails, focus a sum of my chakra into it and lodge it tip first into the ground, I then slowly manipulate the nails to travel underneath my opponent, and once it has reached the desired location, I have it emerge from the ground and into the feet of my opponent, causing him to be off guard and in pain due to the nails making its way into his feet, then I would use that time to attack with a fatal technique to end the battle.
How you will use the technique offensively: I believe this is explained in the above description

.
How you can defend against the tech: I would as soon as the nails start making any sort of movement beneath my feet, which I most probably would feel, and I would just jump away from the nails and sever the portion of the ground where the nails were emerging, this would also most probably cause the chakra to be disturbed within the nails and render it useless for the opponent.
Whether or not you find the technique useful or interesting: it is somewhat useful, if used correctly of cause, but then again it is also not that much useful because while the user is focussing on manipulating the nails, he could leave himself open to an attack.