What do you guys use when writing on balsa?

If I'm after a sharp line, I write on 1/64 ply or heavy paper and stick it to the face of the balsa. If a sharp line isn't required, I use a grease pencil or similar, just something that won't damage the wood

If just making a tick mark to mark where to cut, I just use a mechanical pencil with soft lead. If its something more complex, or putting identifying marks on a piece for future reference, I put a piece of masking tape down and write on that with a pen or magic marker.

I use 4B lead in a .5 mechanical pencil. It's soft, you can't bear down on it like you would with regular lead. 4B will mark the softest balsa.

https://www.amazon.com/Pentel-Hi-Pol...ywords=4b+lead

I have to admit... I prefer a good ball point pen. However I usually cover with fabric and paint so it will never show thru.

I like the ball point pen. I use the cartridge only.

Pen is OK as long as you don't use a solvent-based paint like Poly-Tone. It will dissolve the ink and wick it right up through the covering and it will keep coming up through the layers of paint, no matter how many you put down. I suspect dope may do the same thing.

Never thought about that, I just use hobby store acrylics...

The only time I "write" on balsa, is to mark a cut line. For that I use an extra fine point Sharpie. Eh, works for me.
I also use it to simulate panel lines on electric models.

x2 on the extra fine point Sharpie, as it will not dent the wood. I use a dab of acrylic paint from your local craft store to cover any marks that might show through to the finish (for example, if you were using yellow film covering which seems to let every underlying imperfection flash through).

I also use Sharpies for any markings on covering material. A dab of alcohol on Q-Tip cleans it away easily.

The marks from a Sharpie don't seem to soak into the wood that much. It can easily be sanded off. I usually mark just outside the length I need, cut just inside the mark, then sand to get that "perfect" fit.
I'm getting ready to cover a Sig Rascal with transparent orange Monokote so, no marks allowed! And yeah, after using yellow Ultracote on a G.P. Skybolt, I've sworn off yellow altogether.
Hey, has anybody figured out how to get paint to adhere to Monokote? I would prefer to completely cover the Rascal, then paint on the trim color.