Such a list of events in sequence gets a bit boring if you use the same structure again and again.
Sometimes this is good for clarity or emphasizing repetition.
There are several structures to express this kind of thing in Latin, and here are some:
- A temporal clause: Cum rem primam fecerim, rem secundam faciam. "When I have done the first thing, I will do the second thing." If you use cum, you must observe consecutio temporum rule regarding the tense of the predicate in the temporal clause. The rule has been discussed on this site (e.g. here), but feel free to ask a new question if something puzzles you.
- A participle with a preposition: Post rem primam factam rem secundam faciam. "After the first done thing (= after doing the first thing) I will do the second thing." This construction does not appear as such in English unlike the previous one.
- An absolute ablative: Re prima facta rem secundam faciam. "The first thing being done, I will do the second thing." This is a very versatile and confusing construction, and there is no proper English parallel.
- You can say "then": Depending on context, that might be deinde, denique, ergo, tum, tunc, or something else. In my opinion deinde is the most neutral temporal "then". The word post is not really suitable for this use, although it can be both an adverb and a preposition.
- Use the future perfect for the first thing and the future for the following one.
If you want to indicate that you were the one to do the first thing, you can add an agent to the participle: Post rem primam a me factam or re prima a me facta works fine.
I might render your little story like this:
Rem primam vobis describam et deinde secundam. His descriptis rem tertiam describam. Has omnes cum vobis descripserim, postremo rem quartam quoque describam. Et, ut bene discatis, post descriptiones meas omnia vobis repetere oportebit — nisi obdormiveritis.
I will describe you the first thing and then the second one. Having described these, I will describe the third thing. After I have described all this, I will finally describe the fourth thing, too. And so that you learn well, you will have to repeat everything — unless you will have fallen asleep.