On Mon, 12 Aug 2019 09:56:37 +0100
John Rumm wrote:

On 11/08/2019 21:56, Vir Campestris wrote:

Ever try painting inside a 1/4 inch wide groove, deeper than it is
wide, without getting paint on the edges? I ended up using a model
makers paint brush

Perhaps some clear spirit based cuprinol might have been a better
answer
- just pour/spray it in!

And follow it up with a coat or two of clear varnish.