I've been using NAT for a long time and this the first time I've seen the terms DNAT and SNAT. I had to go look at Wikipedia.
To help you, pay attention to Wikipedia when it says "This use of DNAT is also called port forwarding". I've only ever heard it called port forwarding. The keyword you'll want on your rules is "rdr-to".
Wikipedia points out that SNAT is used to mean many different things. With what you said, I'm assuming you are using SNAT in the sense of Source NAT.
What you are referring to as SNAT is what PF means when it uses the rule modifier "nat-to".
I don't know which tutorial you might have used, but the definitive one is at http://home.nuug.no/~peter/pf/ by Peter Hansteen. He also recently released the "Book of PF", which I own and is quite good.
PF can be confusing if you are coming from Cisco (or other) nomenclature. I know this because I got rather confused when going from PF to Cisco while taking a class.