Hi,
I use a Griffold Hobby Knife with blades which are razor sharp and go down to a oint.
The trick with cutting thick card, or for that matter, any card, is to take the first cut as precisely as possible - like scoring the card, if possible alongside a safety ruler - Maun make a great one and it keeps your fingers well out of the way of your knife blade.
Then you take your time and do multiple cuts - the idea is not how quicly you get through the card, but how accurately you do it. After a while. cutting card is real easy.
The Griffold Knife is held like a pen, so you are not applying the same pressure you might with a Stanlet type blade.
Lighting is important. Make sure you get plenty on your work area, but not too harsh. If you don't your eyes will be the first to go.
When you begin making a warship model, don't think in terms of how quickly you will get it made, but how accurately you are going to make it. When you build your next model, try to improve on your technique and learn patience - don't be distracted by what is going on about you.
My 1/200 Bismark model took me 18 months to build. Other warship models average out at 6 months each, that is in terms of hours spent on the task - 8 hours one day, a few hours the next and so on. The trick is to make your mind control your body and get your head and hands on the model, then it becomes easier. sometimes it is as if your body is fighting you.........ever had that experience?
hope that helps,
J77ason