Would appreciate any recommendations on what is a good thinning agent for Jarrows Inletting Black, not sure what to use.

I put a dab of Jarrows on a sponge in a dish then pour a little motor oil on top and smear it around. Then I use a brush to dab on top of the sponge then to the part being inletted.
Phil

I use it as is but put it on very sparingly. I use an acid brush and spread it on the metal just enough to give a mark, if you put it on thicker you get a lot of false contact points.

Just buy a tube of black artists oil color. Mix it 50:50 with petroleum jelly. Cheap, won't get thick. Lasts forever.

I am just copying what I saw inletters do at Bishop and Fajen years ago. Figured they knew more than I did (everyone else does)
Phil

Birchwood Casey makes a synthetic oil that I use, however it does seem to "dry out" some. Sone type of oil any way

Never had to thin it yet but I would be inclined to try something like mineral oil.
BB

I have used a Zippo lighter for years and it works fine without the oil with a smoke base. A candle will work just as well and cheap to buy. Smoke was used and might still be used be people scaping to true up old machines. Why waste your money on something you probably have in the shop.

I had a can of low odor mineral spirits on hand and it worked out fine. Got a nice thin layer on the metal, which in turn prevented getting a false reading and removing too much wood, kind of a now I get it moment for this amateur.

I use a few drops of lighter fluid dropped in to thin it; put it on in a thin layer using a q-tip.