Recently moved into a \~100 year old home with plaster walls. Previous owners put a bunch of holes in the wall to hang art that left a number of cracks in the plaster, so I want to use picture rail going forward to hang things.

There is a run of picture rail molding beneath a larger scalloped piece that at some point had the gap + area behind it filled with a mix of plaster / caulk / paint. I considered just completely replacing the molding, but decided to try to unclog the gap. My current method has been:

\- Use a putty knife + hammer to break through the top layer of paint and crumble some of the plaster to reveal the bounds of the gap (there's a pretty clear line beneath the top scalloped part)

\- Use an oscillating multi-tool with an all purpose attachment to clear out the gap

\- Sand the area down with 80grit sandpaper to prep for painting, and fill any nicks in the molding with dry dex. I'll eventually repaint it to make it all look nice.

In addition to being slow and exhausting, the result looks pretty messy and leaves shards of what I believe is plaster behind the rail, which interferes with hanging hooks. I try to scrape out as much of it as possible, but the larger pieces get lodged pretty good. I'm also worried I'm knocking out the plaster from the wall behind in addition to whatever was used to fill the gap. My only option is to slice it up with the multitool, which is hard to control and I often end up cutting into the wood above / below.

Is there a better way to do this that is (1) faster (2) leaves a cleaner result (3) doesn't damage the wall behind? Is knocking off the plaster behind the rail a big deal? I'm worried if I ever try to replace the molding it'll all come crumbling down.

Restoring Filled Picture Rail - Is there a better way to do this?