The way I do sankyo from yokomen is to enter with irimi, deliver atemi to uke's face with my right hand, blend at the yokomen hands wrist with my leftwrist and then reach over and take the hand in sankyo with my right hand and apply the technique.
For ikkyo blend with the attacking hand and follow inside of uke in a circular movement until you have redirected his yokomen past you. Still keeping contact then apply tenkan ikkyo.
I dont know about nikyo, it's a technique i would never apply to a yokomen unless told to do. Much easier to project someone with a shionage/kaitenage/sumiotoshi or something.
I believe yonkyo could be applied in the same way as the sankyo accept of course applying yonkyo instead of sankyo
Alternatively you can grab ukes fingers and push them back into him so that he has to drop to the floor or have his fingers broken and then apply yonkyo onto his unprotected arm.
Thats the way I do em, seems to work.