Problems with css changes not being propagated

I’m making changes to a theme I built using WP Starter in v2. Now I’m on v3. I’m finding that some changes that I make in a stylesheet are showing inside Pinegrow, but after I export the theme, they aren’t making it to the test bed all of the time. So far I’ve been able to force the changes but I haven’t identified the pattern of what finally makes it work. So, some questions:

  1. If I’m using SASS, do I enqueue the .css file or the .scss one?
  2. Do I need to do the enqueue only once, in the master (index.html in my case, or in every template (category.html, tag.html etc.)? (I’m guessing just once!)
  3. Is there a fast way to associate a new .scss file with every template, or do I have to do this manually?
  4. What do “Recompile this” and “reload” do in manage stylesheets?
  5. What do Refresh current page (Ctrl-r) and Refresh (in manage stylesheets) do, especially in conjunction with using an external editor to change the .scss file?

I found that I had managed to register the same css (or scss) file multiple times in functions.php probably due to #2 above. After I removed the actions, I find I have none in functions.php (even though I can still see the action in index.html. I’ve tried various combos with de-register and then register and enqueue but I don’t see anything in functions.php. How is this supposed to work, and how do I fix it?

I’m pretty sure that I’m doing something differently, due to ignorance, but at this point I don’t know what else to try. I’m hoping specific answers to some or preferably all of the above questions will help, but I’d also be happy with just an answer to my problem, not getting css changes to the site theme folder.

Many thanks in advance!