I find that opening the hard disk and very very gently twisting(rotating) the read write head with tweezers is the best method, if the frezzer doesnt work of course. the head support is springy and will accept some torsion and get back to position but you must be very gentle and carefull with the small hair thin wires attached to the head. if the drive makes a grinding noise its possible to twist and bend the head slightly until the noise disappears and then low level formatting the drive afterwards, i did it a couple of times with sucess. it may work while making the grinding noise but it will scratch the platter is short order and go dead so watch out for that..head to platter noise is different from bearing noise it is very high pitched almost like scratching nails on a chalkboard....
i have had great sucess with that method but you have to be very gentle and it doesnt work when the bottom head is also stuck because you cannot get to it...on the bottom head maybe use a toothpick for example...but usually the top ones are the ones wich get stuck.....trying to spin the disk by hand to free the head is tempting but will result in catastrophic failure 99 out of 100 times...dont do it please!!!dont worry too much if you damage the platter a bit or if it is stained were the head was stuck, it will often still work if we are talking about old mfm drives and depending on the area where the damage occured....if you leave a fingerprint or dirt on the drive you can ultimately spray it with brake cleaner, yes it sounds weird and extreme but it works, cleans the platter and leaves no mark or residue. dont use a cloth, cotton swab, foam swab or anything mechanical to touch the platter to clean, if you need to clean just spray it like i meantioned, it works. if its only dust you can blow it with a can of air but if you need to clean marks grease or stains use brake cleaner... i have some perfectly working drives that were stuck and had the same "treatment"...now what i dont know is how to prevent future stiction problems....maybe the only way is to remember to plug the drive in every couple of months or so.
i have a passion for old hardrives, for me an old computer with a xt ide or something like that is not desirable...i like the hard drive more than the computer itself especially old stepper drives...dont know why though...lol unfortunately they are getting rare expensive and fragile so try to be as gentle as possible and if ot doesnt work just close it and keep it...unlike IDE, on mfm drives you can swap boards for example..if its the same model it will work without any mods....or maybe in the future you can gain other skills and fix it in a different way...anyway if you cannot revive it try to preserve it as intact as possible