I scan at 600 dpi and use the basic 8bit grayscale settings then use levels in photoshop to even it out. If some of the inking/feathering looks wonky I’ll dodge/burn it. Then I save as a bmp tif at 50% threshold.
The other thing is that I usually “try” to work at 100% of the printed final. For 18x24 posters I work at 11x17 which is as large as my scanner bed. Enlarging it to the poster size works pretty well and I retain the clean and sharp lines.
Hope that helps.
Flight got delayed. Stuck at the airport for another 2 1/2 hours. So exhausted. Wonder if I should stay an extra day. Ugh…