For the ReDrum and NN-XT machine I assign each channel to a channel on an extra mixer and then assign the extra mixer to the main mixer. Sometimes, e.g. with different violins samples on let's say 8 NN-19's, I may assign each of those NN-19's to an extra mixer too and then assign that to the main mixer. It works a bit like a bus then because when I have set the volume and panning for e.g. each drum on the extra mixer then I only need to move one fader on the main mixer if I want to fade the drums in or out etc.
Also, I guess you also know that you should assign reverb and delay to the mixer(s) and not to each instrument and then just add reverb and delay via the knobs above each channel.
Also, sometimes, I add a compressor and the 2 band parametric EQ between the main mixer and the midi in device/sound out. That way you can EQ and compress the beat as a whole.
Turning Reason around and seeing the instruments from behind gives you many options where you can assign stuff through another instrument etc etc and add different stuff our use different outputs/inputs.
What I did back with 1.01 and am now approx. halfway through with 2.0-2.5 is reading the whole manual from start to end whilst trying each thing out in Reason...and then just play around a little too.
When your finished with your beat, export it as wav. and try to play around with your different plug-ins in your CEP, SoundForge or was it GoldWave you used.
None of this will make you and I engineers or be able to master our beat to perfection but it it can only help.
Another thing, when adjusting volume, set the drums first and then try to lower each instrument individually until you can't hear it and then increasing it again. That way you should get a better feel on how loud it should be thna you would if you just e.g. lowered a little from volume 100 and until you thought it sounded right.
Last but not least, I always say less is more. If your sound needs lots of reverb and delay etc to sound good, then it isn't the right sound...hard to explain but I hope you know what I mean.