As I've mentioned in a couple of recent posts, Tomiki atemiwaza is not really like most karate atemi. Aikido atemi can be seen as more of a whole-body push than a strike. One interesting thing about pushing against the opponent is it gives you two possible actions. Take shomenate, for instance. In shomenate you typically evade inside and push uke down backward by pressing under his chin or on his face. But another interesting and useful action of shomenate is to push yourself backward off of uke. We call this the 'aiki brush-off' but all it is is an instantiation of that physics principle about 'equal and opposite reaction.'
I teach aiki brush-off as the first, most fundamental form of shomenate. I tell students their initial goal is to evade inside, get both hands up, and push backward from whatever they contact (hopefully face) so that you end up outside of uke's reach. Then the classic shomenate becomes a backup condition - any time you're unable to push backward off of uke, use the immense leverage you've developed to jack uke into motion backward away from you.
Patrick Parker is a Christian, husband, father, martial arts teacher, Program Director for a Cardiac Rehab, and a Ph.D. Contact: email@example.com or phone 601.248.7282