Reddit mentions of The Army Painter Anti Shine Matt Varnish for Miniature Painting - After Quickshade Matte Top Coat Acrylic Varnish for Miniatures - Matte Finish for Acrylic Model Paint, 18ml, Dropper Bottle

Vallejo Matt Model Color Varnish, 17ml https://www.amazon.com/dp/B000PH9JPA/ref=cm_sw_r_cp_apa_i_4ZWqDbN193MQG is a good one.

I use The Army Painter Anti Shine Matte Varnish https://www.amazon.com/dp/B007QW3M0U/ref=cm_sw_r_cp_apa_i_z1WqDb9D0KQZX. Because they had it at my local shop, it dries fast and I like brushing it on to control the thickness and honestly it doesn't take long.

Before you use a matte varnish use a gloss one it's a better protector. I do 2 thin coats of gloss then 2 thin coats of matte.

Gloss varnish- Vallejo Acrylic Paint, Gloss Varnish https://www.amazon.com/dp/B001JJZDSK/ref=cm_sw_r_cp_apa_i_82WqDb58V9HGK

Yeah varnish can be weird, every brand is different I use to love this reaper brand but can’t find it anymore but the army painter stuff I’m using is a close second.

Hobby Anti-shine Paint Pot https://www.amazon.com/dp/B007QW3M0U/ref=cm_sw_r_cp_api_i_UcRPCb3HW1Z6P

Then you have peeps who use unconventional types of varnish like pine-sol or something like that through an air brush. Although I can’t remember if it was pine-sol that I read that they used. I think it’s weird but if works for them to each their own.