Basically with oil finishes, such as pure tung oil and boiled linseed oil, you apply as many coats as you feel like applying to develop the build you want. Neither of this type of finish will develop a gloss. One old suggested guidance for the application of boiled linseed oil, which you can apply to pure tung oil was to apply once a day for a week, once a week for a month, and once a month for a year. For my money, this is a bit excessive, and I reckon you can get away with anywhere between about two and five coats applied over about three to five days. Application is to wipe or brush a generous coat on, leave to set up for a bit, say ten or fifteen minutes, and buff off. Leave to dry. Repeat until you've got the appearance you're happy with.
I'll assume you're not aware of the fire risks associated with the careless disposal of rags after using them to apply these finishes, and if you are aware of them, I apologise in advance. Rags used with these drying oils can spontaneously combust, especially if they are scrunched up in a tight ball. So, after use, lay them out flat on the floor, or put them in a bucket of water, or open them up and hang them out (a bit like hanging clothes out to dry), or put them into a sealed container to starve the oil of oxygen thus preventing ignition. I'm even aware of people chucking the rags onto a fire meaning they're working on the premise that they know the rags are burning and can monitor it - not sure I really approve of that last tactic, but I've worked in workshops where that was fairly common practice.
On the other hand, you may be talking of applying a tung oil finish, a teak oil finish, Danish oil, or similar, all of which are essentially a soft oil based wiping varnish. With these, follow the guidance on the can but, as above, take care with the disposal of used finish application and wiping rags. Slainte.
