If Trump is half as smart as he thinks he is, he would have had some kind of auditable process for declassifying documents. He knew The Swamp was out to get him. It doesn't have to be an onerous process, but it should be *something*.
Just saying "I declassified that" should be enough to provide reasonable doubt in a criminal case, because perhaps he really did. If he had a subordinate enter into a ledger the document titles and the date and time they were declassified, that would give him a political defense as well. Or just a rubber stamp that said "DECLASSIFIED" for the first page and a place for his initials.