Tiger,
I am going a different direction than the fewest number of coats on this post. "Sand Through" in spots is often indicative of what we often refer to as "Out of Round" which is not necessarily the "correct" term, but more or less the common use term.
If you have calipers, measure the diameter of the pen and then rotate the blank about 45° and measure again and then again at 90° from the original measurement. Then do this in the middle and again at the other end of the turned blank. This will show if there are high spots and low spots.
If you have low and high spots, "sand through" will occur on minimally coated blanks.
The reasons for OOR can be several:
1. bushings on occasion have the hole bored off center by .01mm or so;
2. if using a mandrel, the mandrel can flex if too much pressure is applied with sanding or turning tool;
3. using the wrong tail stock live center (must have a 60° live center with a mandrel.) The wrong tail stock will cause wobble and OOR.
4. too much pressure in sanding - combined with soft wood sanding quickly while hard grain side does not.
5. pulling the tail stock up too tight (you don't want to leave it loose,) but too tight will force a mandrel to flex or wobble.
Since 4 of these deal with mandrel problems, many turners switched to Turning Between Centers, often referred to as TBC, which does not use mandrels.
The blank should be perfectly round when measured with calipers before applying CA or other finish. This does not deal with the CA application referenced in your link, but the work that should be done prior to the application of CA, particularly if you want to use the least amount of CA needed.
BTW, you didn't say why you wanted to use the minimal amount, but using the least amount is dependent upon each individual turners habits. I use less by not applying with paper towel. PT will absorb up to 90% of the CA while putting 10% on the blank. Some people use the small parts bags that pen parts come in; put that on your finger and apply a drop on the bag and rub it onto the slow turning blank. Smooth the CA flow down the blank. There are other applicators that do the same and do not absorb into the paper towel. For me, I get a more even and consistent flow of CA on the blank with a plastic or foam applicator than I do with paper towel. I still use PT on occasion just because, but most of the time it is with a plastic or foam applicator.