Pretty must most the stuff is covered in those 2 articles. You can't really go wrong there. One thing that i would advise is to yes get as many progressions and drills and you can, but only work with 1-2 at most. This skill isn't so hard to actually learn, what is hard is to do it nicely. It requires good conditioning.
Work lots of press to handstands on a single rail bar. Starting with the gymnat standing on the bar in a staddle, they lean forward to they are falling over (you are there to stop them of course). From this position (which is similar to them coming up from the stalder) have them press to handstand as you help them move (simulating the circling of the skill).
You once you are comfortable with that and the gymnast can do as well. Have them do it on the low bar. Exactly the same, but on the low bar. You will spot fromt he shoulders not the waist. They need to learn and rememer to keepthe leegs pulling in and not rushing the circling and closing the legs.
On the metal bar work lots and lots of Clear staddle sole circles.. They need to learn to pull drive the shoulders down and, turn upside down. Good place to work the key positiosn
1- the Entry
2- The vertical bottom. ( a nice flat pancake, with back parallel to floor)
3- The ascent ( but leading, legs held in tight into armpits)
This drill progresses to Clear sole cirle to straddle stand on the bar..then jump press to handstands.
Then she can do the press a little earlier and not let the feet touch the bar.. and work it up to handsstand that way.. Drills works well as an independant station.
But yeah work lots of on the entry..such as the drill in the 2nd article.