Paint pens

[losinground]

Are there any paint pens finer than extra fine?

[Tamiyabigstuff]

How fine are you looking for ?

I've seen paint pens as fine as 0.3mm

Just do a search on ebay for 'paint pen' and see if anything looks suitable for your needs.

[Prescient]

Which colour and brand are you looking at as some extra fines are not really extra fine by other standards?

In my experience, due to the way good paint markers deliver the paint (oil based / permanent) via the tip you can't get anything functionally finer than XF and beyond that you are better off using traditional painting techniques. Most paint marker XF are 0.7mm to 1.0mm tips but Faber-Castell go to 0.4mm and Pilot Super Colour to 0.5mm. It depends on the colour too.

If you need gold or silver metallic or white then the Pilot Super Colour is the best in my opinion. For regular matt colours you have more choice.

Sakura Pigma Micron go to 0.2mm (005) but are really a fine liner. 

You can get down to 0.1mm on the fine liners but you need to check surface / base material compatability as not all will work or look good on anything other than white/grey primed surfaces. 

Hope this helps and if you are uk based I can recommend cultpens as a good supplier. 

I have found a lot of paint markers / fine liners are only really good on paper for artist use so pick carefully.