Tenses in flashbacks within past-tense stories



Argh I'm done trying to figure this out by myself and the internet confuses me with the names of tenses. Perfect, prefect, participle, gonorrhea!!!! I am not writing an exercise book! Please, please, help a girl out without text book citations, because, at no point do my characters discuss grammar... So here's my problem:

I'm writing in 3rd person ltd., and in past tense:
He went outside to hammer the cat to the tree.

Now, there are some flashbacks:
He had found that cat on his way to hammer his sister.

At what point can I drop the "had had had"? If this were the second sentence:
The creature was blocking his way; he would have had to swerve about two inches to the left.

Or must I:
It had been blockhing his way; he had had to swerve and borrow a flame thrower to murder English grammar.

Can I, like, do the first sentence of the flashback with the "had found the sinister hairball" to establish a past-past-tense, and then just go on in regular past tense? Like the rest of the story? And then end the flashback with a new paragraph in which the first sentence contains what the reader would expect in the "present"/main story line?
Or do I really have to scatter hads everywhere throughout the remembrance of past times during a past tense narrative? Or can I at least drop the "had" after a short-ish introductory-to-the-flashback paragraph if not after 1 sentence?

Thanks in advance :hooray: