You just have to add two numbers. With the big number hand you can count hundreds by using the closest segments first, then medium then distant and so on. Hardest additions will make you carry the one once for a case like 19+175 which is easy enough. Also, going from 37 to 38 in binary with fingers you have to close 4 fingers and open one while counting segments you at most move your thumb to the next segments on both hands.

Binary still works fine and is better depending on the specific case but in my opinion counting segments is usually more convenient and base 10 friendly.