O.K. just for you ,applicable to YOUR iron and YOUR situation.
Fully taking advantage of the laws of quantum physics and mechanics . . .to further assist.
Yes, I was referring to the new tip, since you seem to be unable to get it to take a tinning.
Plus, the old tip, seems to be nearing the end of its lifespan .
Looking at the tapered, conical end of the soldering tiplet, it appears to extend for ~ 1 cm.
Let's start our tinning approximately 0.5 cm before that tips taper starts.
You will have to figure out how you can hold the irons handle from moving while you are using
both hands to scrape with a knifes blade and apply touches of solder with the other hand.
That could be the use of a vise or some type of clamp, or you could even bind it to something with
a heavy cord or a small rope. Or you could have someone hold it for you.
Considering the use of a sharp pocketknife, since you can always resharpen it or I sometimes use
the two edges of of a single edge razor blade.
Here is how the magic is done :
You plug in the soldering iron to start its heating then you scrape the metal 0.5of a centimeter before
the start of the conical taper, which will let you see exposed shiny metal below it.
Touch the cleaned area with solder to see if it will melt, if not, keep scraping and touching until solder
melts and adheres to the scraped area. As solder progressively adheres and tins, move the scrapes to
the side and down the taper to create an ever larger tinned area.
CLARIFICATION:
The scrapes need to be made towards the tip of the iron . They need to be made hard enough to expose fresh metal. They need to be made in a single movement. Not having the blade in constant contact and making back and forth movements on the tip, as that will unnecessarily carry away needed heat into your knife blade. ( Not to mention the adverse effect on the tempering of the blade .)
After you get a blob of solder to tin onto the triplet, you will find that the solder will be carried forward with the knifeblade scraping to adjunct newly cleaned areas..
This is about the time that you will be thinking, WOW this is working so well !
BUT, that is really the time that you need to reach over and unplug your iron, excess heating is going to be detrimental to your fresh thinning.
So you work with the " flywheel" effect of present heat until the point where you see the solder starting to be sluggish from lower heat.
Then you plug in the soldering iron again to get the temperature back up to normal solder tinning action.
Using this cycling of iron temperature should let you tin the whole tip. . . .without letting excess temperature
burn away your new tinning and blacken the tip.
That can happen later if left in its stand and not being used.
Forgot to ask . . . .since you were able to get heat sink compound . . . .can you get any liquid rosin
soldering flux ?
OR . . . . are we going to have to direct you to a violinist and a bottle of isopropyl alcohol.
73's de Edd