Well it depends on the sounds and quality of the sounds. If the violin has a high mid problem, I tend to use a linear phase EQ, because I know I'm going to use a lot more EQ down the line, same with viola. Over the EQ I will tend to place a tape sim for volume leveling...I use the J37 from Waves, but you could use Sonar's pro channel variety or even Wave's master tape. I then place Waves NLS summing plug and send that into a buss with a compressor...something tasty depending on the NLS setting. So if it was a Beatle type track a Fairchild. Oh and I forgot, I tend to use a double fx, either Wave's Doubler or Wave's ADT.
For brass I tend to use a tasty EQ, Wave's V series EQ is good. I also like the Redd EQ for a simple EQ, I then tend to send the individual brass tracks into an Aux or buss where I will EQ again, I will probably use a tasty compressor the VComo or SSL by Waves and probably a J37 again...not in that order though. Oh and an NLS summing plug.
These are just basic settings, I tend to mix it up a bit depending on the sounds and track. I also like to double the string instruments with granular versions of themsleves. And Wave's CL2A is great for anything to do with strings...even mastering. Oh and sometimes I will use Wave's Brauer plug to move things about in a 360 degree field.
It might sound like a lot, but...it works and It's how the rock avant-garde or their production team did things...layering.
Sorry, I use Notion 6 for my orchestral instrument - and in fact all my midi sequencing these days...but I tend to do some edits of midi in Sonar.