One other option is to use MDF hexes and glue them down onto boards. I've done this a few times and just come across link via Mikes site that has the mind racing.
You could also make a template and mark the corner dots or go full lines such as link
The problem with all of the above is handling roads and rivers that are sunk below the field level. There is a guide for the Kallistra hexes that involves flipping them over and filling part of them link
If you do use the Kallistra one – get the flocked version. I've tried getting as neat a result and failed and still have to do my big pile of Heroscape boards. See link for ideas on the smaller Heroscape boards.
One very intriguing tool I'm considering is hexterraintoolkit.com – not a five minute task though.
Currently, I'm playing with sticking foam on top of link – not a great result so far but it would be easy to add hex corners on to them or maybe mask the actual lines off while building / flocking Themis you keep then 2D.
Have you considered mats with hex overlays?
You could also try asking totalsystemscenic.com to see if that could add lines to their boards if you do not feel up to it.
