Hi. No personal experience with a Miroku stock, but I've given some TLC to other stocks of fellow shooters, mostly Brownings. If you want to completely re-do the finish, I'd recommend sanding and building up the finish of your choice by adding thin layers. One after the other is dry, polishing in between to rid any imperfections. I think boiled linseed oil would best be used as opposed to raw linseed oil, but linseed oil (same for Tung oil) takes many many layers if you want a really nice finish. For 'maintenance' I'd (clean thoroughly and then) use the same product that was on there and apply a thin coat, polish down with microfilm, 000 steel wool or just a really vigorous rub with cotton.
Personally I like a glossy looking finish with a tad less work, and Tru-Oil ticks those boxes. Wouldn't use it on an existing finish (that wasn't tru-oil to begin with), but at least if you do it yourself you always know what's on there.