Help with combining Ha and OSC from a different session

Hello all - I've purchased APP and I find it quite useful for simple single and multi-session work, gradient removal, Ha/OIII extraction etc. when all of the sessions are of a similar nature (e.g. they use the same filter).  I may not know how to ask this question very well, so I will just state what I am trying to do and I'm looking for some clear direction (don't assume I know all of the inner workings of APP - I just basically take all of the defaults and let APP do it's thing and I hope it is correct).

I am using a Fuji camera with dual wavelength narrowband filter for the Ha signal generation and the same setup minus the filter for the "OSC" color information.  This is for nebula processing.

I have two sessions of images collected with the duo-NB filter and I want to extract the Ha signal, which I know how to do.  I also then want to process another (third) session of data that was acquired with no filter.  I'd like to use the full color image from the third session and boost the red channel with Ha from the first two sessions.  I know about the combine RGB tool, which I have used for Ha-OIII extract Ha/OIII type HOO re-combinations, but I don't know how to do what I am now trying to do.  I'd like to try to do as much of the work in APP.  I know that it is possible to simply process session 1 & 2 together and extract the Ha signal and then perform an Adaptive Airy Disc integration of the third session separately and then fiddle with the rotation in Photoshop and do channel manipulation and layer blending to get the result I am trying to achieve (if I can figure it out - ha!), however, I'd like to see how far I can use APP instead of leaning on Photoshop so much (I'm not a Photoshop expert either).  Can someone explain to me without assuming I'm that I'm a world class APP user how to do this?  Thanks!  

Edit:  Perhaps this is what I am trying to do:  https://www.astropixelprocessor.com/community/postid/7610/