So we've just begun it. Some of the more difficult things are:
1. remembering the weirdness with forms, especially since the patterns aren't necessarily immediately noticeably consistent.
2. visualizing the purposes for each of those tenses.
3. hearing the purposes of each of those tenses.
So to combat those, I did the following:
The kids and I told a very basic story on Tuesday - T doesn't wake up. Dog comes in and barks. She doesn't wake up. Dog stands on her. She doesn't wake up. Dog falls on top of her. She yells apage te! (be off with you!) and gets up.
The next day, we told the same story as a memory. I stuck a doll in T's chair and told them it was T, and that the T on the floor was a flashback. We retold the whole story in the perfect tense.
Then we wrote it, in the present and the perfect, illustrated, in our notebooks.
Today, I had the boys narrate the story in the present. We made a big deal out of T being in her chair and the story not happening right now. Clearly we should narrate it as something that happened Monday! Every time they said a verb, the girls stopped them, shook their fingers, and said, "Prave dicitis. T dormivit" with a finger snap behind the head (to indicate perfect tense), and the boys repeated in the perfect. On every sentence.
And then they switched. We had T lie on the floor and the dog come in, so it was obviously happening right now. The girls narrated in the perfect, and the boys stopped them to correct them to the present.
We are visually illustrating the differences between the present and perfect tenses, and we are hearing them contextually next to each other, so nothing is in a total vacuum.