One counter punch is the most efective teqnique against another one, specially if the one that punches is very skillful in the matter, remember good punchers are fast and never loose balance and so do not put themselves in an aikido-teqnique-like situation.
Maybe so javi-o, but it remindes me of a story from Aikifaq.com about this seminar with different MA:iests. This Karateka (And I do beleave they can punch) asked this Aikidoka about how to handle multiple punches. The Aikidoka told him to try it on him, which he did and ended up on the mat with a breakfall. The Aikidoka asked him why he didn't threw the x:nd punch. The stunned karateka said that as soon the Aikidoka started with his (kotegeishi I think) all thought of a x:nd punch was vanished. All hi could think of was how to regain his balance
, wich of course hi didn't.
To answer the first question raised in this thred - this week we've trained against ski's with and without tanto. And what we focosed on specially, was being totaly relaxed in your arm closesed to uke in e.i kotegeishi, i.e the hand that (in our cases) blockes and goes from the elbow and down to grab the ukes punching hand - just incase uke pull it back with the speed of lightning. We have a nidan karateka in our club who is a hot as uke when we train this.