Sometimes, I only use soft pastel - sometimes hard for the initial sketch, with soft pastels on top.
I use Rembrant or Rowney pastels and Derwent pencils for mainly outlining and fine work.
The pencils, though, are not strictly necessary... you can always break a tiny bit from your soft pastels for fine work.
Although Rembrandts are generally classed as soft pastels - I'd put them at the very hard end of "soft."
However, when you look at the extremely high standard of Jennifer Blenkinsopp's work, you can tell that they obviously work for her!
Personally, I much prefer Schmingke and Senellier soft pastels. These are in a different class of softness - a bit like comparing glass with butter!!!
I can't find either Schmingke of Senellier pastels in the Philippines, so I buy them every chance I get when I am abroad.
Otherwise, I order these very soft pastels online from MisterArt.com - and have them delivered by FedEx.
(Mister Art's prices are very reasonable but I find that I get stung by the customs on delivery...)