Dots and dashes are only needed if you need clarification in transcribing the notes. I NEVER use them. I didn't want to bother with learning them and they were only mentioned at the beginning. You will find them later in the manuals on occassion, but rearly needed or used.
For example, if you have the word "coat" and "cot", that is written exactly the same way, but a different vowel sound. If you choose to, you could add a dot or dash to one or both of the words so you know which one is "coat" and which one is "cot". This way you won't be wondering what a camping coat is... but know it's a camping cot... (I read 2 letters with that outline in one book and was confused on the second letter about camping coats... , then I realized they were talking about cots. Even that book didn't use the dots or dashes.)
You may have a letter or article or something that talks about "it's cold where you'll be camping, so you need a coat. Your camping cot ...." and actually use both outlines in one dictation practice.
Simplified does not teach this at all. I think it would not get used much, but there are times I want a way to show a word has a long vowel sound without having to write that letter into the outline. Like in the DM or TN stroke.
I think they are helpful if you have time during dictation to add a few marks for clarification. I figure if I just mark the long vowels, it would be easy enough to figure out what the short vowel words are. I don't mess with the short vowel sounds marks at all. Marking those correctly would make me stop and think too hard about what sound the vowel is making.
This can work if you find that you have 2 similar sounding and the same outline for the words.
For example, I was reading a shorthand book (Gregg Dictation and Transcription; Gregg Shorthand Anniervary edition; it's the black book with red lettering), it had a letter early on about coats. Very simple outline c-o-t-s. Then later I read a letter about camping. I thought they were talking about "camping coats". After half way through I realized they were talking about "cots". Yes the thing you sleep on. Same outline for 2 different words. And unfortunately I didn't think the shorthand written in this book was very clear.
If I had wrote it, I'm sure I would have known, but reading it, I didn't. It didn't take me very long to figure it out, but I was still confused...
So if you are writing about camping cots and camping coats, you may wish to use these symbols so you don't get confused when you're transcribing.
"Gregg Shorthand had achieved the most extraordinary success ever attained by any system in the history of shorthand." John Robert Gregg, 1922
There are a few instances where these marks are essential. One rather uncommon case is in distinguishing the words "oh" and "of"; use the dash under the o for "oh". Another much more serious and common case is to distinguish "immigrate" from "emigrate". Both are written e-m-e-g-r-a-t (at least in Simplified and later; maybe also in Anni?). Use the dot under the first e for "emigrate".
By the way, I've occasionally seen a mark for the short vowels used, even though it's not "official". It looks like a micron (or Gregg word-joining sign, or the bottom of the letter u, or the bottom quarter of a circle), and just like the dot or dash, it's written under the vowel. You could write this curve under the first e in e-m-e-g-r-a-t to make it say "immigrate".
1. Vowel marking kills speed 2. Vowel marks are crutches (you use them because you feel not able to read back your shorthand without them) 3. They clutter the outline (as well as the page and notes) 4. They waste time, thereby deterring progress 5. They increase difficulties (writing, reading, transcribing) 6. They make transcribing harder (in transcribing, you have to figure if you meant to use a dot or dash).
You can use them if you need to mark the vowel. Like I said above and as lvw said above, if write, or you know or realize you've written two of the same outlines (for example, "she put the coat on the cot", both coat and cot have the same outline--however you will figure it out by the context). Or it's a name and you write it in shorthand, you may wish to mark the vowel(s). You can see from my above post I came across that and it's stuck in my mind all this time. I doubt I would mark the vowel, but it might help if you aren't going to transcribe your material. Besides lvw mention of "immigrant" and "emigrant" my "cot" and "coat" another example is "glass" and "glaze". There are more, but these few should help you see if you decide to use them.