Most of the time you will see chunks of rubber flying off. I have thrown countless treads or as I call em "gator backs", but never actually "blown" a tire. (My inner carcass was still holding plenty of air, just the outer tread and belt came off. )
I've always felt a slight vibration, like hitting the rumble strip on the interstate, or a few bumps like on a washboard road. Then a few seconds later rubber shrapnel flying and quite visable out my side mirrors.
I think most of the time if you keep your eye in your mirrors, you will be able to catch it before your tire is completely off the rim, on a true blowout.
Just make sure you have a jack and lug wrench or impact, and most lugs on trailers are 3/4" or 13/16"- just fyi
MillerTime- Future Sabre Handler!!