Oh wow, I'm so happy you made this step by step, I've always wanted to see what your rendering process looks like! To any commenters unsure of how to get from step three to step four: there are some great "black-and-white to color" tutorials out there if you search for them and I've been using a few different ones to try and work my way through mimicking joinjump's steps that have really helped!
I'm trying your method now, and I realized, I have no clue what you mean by light filters ;; Are you talking about the filters menu in photoshop, or the "multiply" option on the layers type? Or perhaps, something else entirely?
oh yes, i totally agree with overlay, people say that i use overlay but it always turns out "overcooked" as you mentioned. Ohh, i guess i'll have to discover this other method, okay i'll take not of transparency, thank you! I was stuck with this [link] and so,i'm pretty much lose on what to do and overlay is really bad.
You make a new layer on top of that. Have you ever worked with oil paints before? Well the process is similiar only on the computer. Use pure color, don't have it darkened or anything. And color it in on that new layer. once you have you can do one of two things. Go into filters for that layer and find multiply (if you did it right it should look nice) Or go into opacity and lower it down to about 75-85. I recomend Multiply.