I learned how to do LRB imaging using RonWodaski's "The New CCD Astronomy".
When I first started with my DSI Pro I did basic RGB processing using Autostar Suite Imaging Processing (ASIP). To make a long story short...
1) Acquired the source images. Save all uncombined images as FITS.
2) Using Envisage offline I'd preview the source images to sort out and delete the bad ones.
3) Load the useable source images into ASIP as a group (one group for each color). Do a one- and two- star alignment, then median combine them, save the result as a FITS. From this I'd get one combined image for each color.
4) Load the R, G, and B images into ASIP as a group and align them (usually just a two-star alignment unlss the alignment was way off to start with). Now I have three aligned R, G, and B images.
5) Using RGB Merge I'd load the R, G, and B images one at a time as as I did so I'd set the blak and white points using the Std.Dev. (Standard Deviation) function. This usually works fairly well. For more advanced work I'd set the black and white points manually.
6) Save the result as a BMP.
Since getting Photoshop I still use the same basic process except step 5 is done in Photoshop, I still use Envisage/ASIP to align and combine my source LRGB images.
-John