It works. Got that advice on here years ago and its my go to. Im outdoor too so its a must for me. And you can spray while in flower which is convenient.
And I am not talking about spraying one time and having the job done. The iso burns the mites and you will still see eggs. Spraying every few days for a couple weeks does the job. It is nice to eliminate the mites completely but growing outdoor the goal is to keep them at bay and get a harvest. Growing outdoors you will always have to deal with pests and never be able to eliminate every pest. ISO is the only thing I will spray on the plants. Been doing this for years. You can search it on here and you will find a lot of reputable people do this.
Boy I hate spider mites, but they did introduce me to washing my harvest. Have you inspected the underside of your leaves? Their poop is easier to see than the bug.
I moved where my outdoor plot was (away from tall grass), and started using companion plantings. No more run-ins with those jerks.
But now I wash all my outdoor. No matter what. Harvest by the branch, de-leaf everything I can easily snip, wash and hang. The sheer amount of junk that comes off is staggering, and quite frankly gross. It is a pain in the ass, but well worth the effort. Added bonus is an even, slow dry no matter the nug size.