Just a quick question in the vain hope of saving myself some time.

Anyone got any tips on the quickest/easiest way of getting the last bit of paint and primer out of the corners between each plank?

Was going well until now!

Never done it but Model shops sell perma grit sanding blocks in all sorts of shapes. It may help.

use a scraper, either a sharp chisel, or a piece of flat guage plate - good tool shops will sell flat steel scrapers in a variety of shapes, straightedge, curved etc, and you can always regrind to your own profile, resharpen on a stone etc

Old fashioned wire brush any DIY or Motor Shop.

The Griffin............ ?

cabinet scraper, thats it!

Putty stripper. takes the layers off without scraping.

Busty blond stripper sounds a bit more fun!!

You can now buy very sharp scrappers with replacable blades. Same type of blade as an electric planner only shorter... Very sharp indeed.

I think you might be talking about a Scarston Scraper.   The small one about 2" (50mm) is the best and you need to round off the edges to avoid them digging in.  Then make a burr on the blade and re-burr every 4th or so stroke(!)using a saw file.  have fun!