How do I say this in Latin......

[reptilia5]

Salvete! I am teaching my son the Greek alphabet in preparation to begin the study of ancient Greek. We use Latin to learn the Greek alphabet (example: Haec littera (alpha/beta/gamma,etc.) est; quomodo (alpha/beta/gamma,etc.) scibemus?; (alpha/beta/gamma,etc) scribamus; Quid est haec literra? (with proper response);etc. Now I am trying to test him on what letter follows another letter before he see the next letter but I don't know how to say "what letter of the Greek alphabet follows/comes after...(alpha/beta/gamma,etc.) How do I say that in Latin? Also if someone could scrutinize the phrases I am using and give corrections and/or alternate phrases that would be greatly appreciated as well. Another phrase I use when he is spelling from memory is "Oculos clausi et (alpha/beta/gamma,etc.) scribe. According to my dictionaries "scribere" means to both write and spell. Is that correct? I have over one year of Latin self-study but am sometimes a little uncertain about my grammar manipulation. I try my best to make absolutely certain my son is learning only grammatically correct Latin from the beginning. I am aware of the fact that Greek letters are indeclinable in Latin. A big thanks to anyone and everyone who reads and responds to this post.

[Aulus]

Now I am trying to test him on what letter follows another letter before he see the next letter but I don't know how to say "what letter of the Greek alphabet follows/comes after...(alpha/beta/gamma,etc.) How do I say that in Latin?

"Quae littera sequitur alpha/beta/gamma?", using the deponent verb sequor sequī secūtus.

Another phrase I use when he is spelling from memory is "Oculos clausi et (alpha/beta/gamma,etc.) scribe.

"Oculōs claude et alpha/beta/gamma scrībe". The verb is "claudō claudere clausī clausus", "oculōs clausī" would mean "I closed my eyes".