I've heard and tried several different methods. As far as 'denatured' alcohol, never heard anyone using it. Mostly everyone uses isopropol (I use 91%) or Pure Grain alcohol (PGA) for their atty bath. Generally, 15 minutes to an hour does fine. Some take it another step and use a vibrating jewelery or sonic cleaner (don't use the cleaning solution) with the alcohol. Others use Crest Pro Health mouth wash, I got a nasty flavor and stopped that. Some also use near boiling water. Honestly, we each find what works best for us.
If you are still getting SOME hits, then the atty is probably salvageable. I would think that the denatured alcohol might be a factor. I would first try the hot water, blow them out, rinse again, then let them dry over night. Then see how they perform.
I have the sonic cleaner and usually bathe in isopropol for no more than 30 min. Rinse with hot tap water, and blow out really good. Then I'll bathe them in hot tap water with a deture cleaning tablet for an hour or so. Works for me, and the way I rotate my attys, I'll clean 12 or so attys at the end of the week at the same time. (I rotate 4 attys in use every 2 to 3 days). I'm still running on the original attys for my Magma that are going on 4 months old, and have only popped one Joye and one LR
through 'Abuse'. Again, works for me.
There's a thread about 'shock' cleaning using a manual batt or manual pass through. I've tried it, but didn't like it. A couple of friends swear by it. Using the PT and heating it up dry to bake off the crud.