To knock the sheen down in any paint add corn starch, mix it in and strain it. Do test to determine sheen desired. Linseed oil is a varnish and will yellow and build up, look at the lid on an old can. Briwax is a good substitute and is just beeswax and carnauba wax. Get the clear.
Not sure. I used to have a pile of 7024. I am a big fan of arctec 223. That stuff is amazing to weld with and has enough elongation properties to make it good for suspension parts. But you have enough mass any 7018 will be fine.