In advancing my level of modeling and painting I finally advanced to using spray primers and spray paints as basecoats for larger models like terrain pieces.
For the Ophidian Archway, I looked at it and instantly knew that this couldn't be basecoated with a brush-on paint. It would gunk up the detail trying to get in all the cracks and crevices. Only way to properly retain all the detail was to basecoat with sprays.
This was a four-step process. I started with Krylon's Colormaster flat black paint + primer. This was followed by a second thin spray coat of Rustoleum's satin stone gray paint + primer.
After the spray coating was all dry, I took GW's Reikland Flesh Shade and washed the entire model. After that was dry I did a drybrush of GW's Pallid Wych Flesh.
The final result is a nice, layered stony look that is a nice variant from the standard gray that a lot of modelers paint stone in. Since the entire archway is meant to be a stone ruin, you could technically leave it at this point and call it done, it looks great!
I plan to go back in and do some more detailing on some of the carvings, but essentially it's ready for the tabletop right now.
***NOTE!!! When using Rustoleums's spray products, be careful to ONLY buy the "paint+primer" version in either flat or satin, or their straight up flat primers. The satin finish is fine because you can wash and varnish over it with flat finishes any way. But DO NOT get just the straight satin spray paint! Make sure it says "paint+primer". I found out the hard way that just the straight satin spray paint will not cure properly on plastic models.
Some pics of the final results:
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tries out 
