Set expectations honestly
Neat, separated block capitals on unlined paper are recognised well, often above ninety per cent of characters. Joined cursive is substantially worse, frequently in the seventy to eighty-five per cent range.
The reason is segmentation. Printed and block letters have gaps between them; cursive does not, so the system must guess where each letter ends. Every guess is a chance to be wrong.
Individual handwriting also varies far more than any font. A model trained on many samples still meets genuinely novel letterforms.
How to write for better recognition
Use dark ink on white or cream paper, and avoid pencil where you can. Pencil is low contrast and smudges.
Leave gaps between letters and generous space between lines. Descenders from one line touching the next line is a common cause of merged words.
Write on unlined or faintly lined paper. Strong printed rules can be read as underscores or hyphens.
Correct the output efficiently
Read the extracted text with the original beside it rather than from memory. Handwriting errors tend to be plausible words, so they do not stand out on their own.
Names, dates and numbers deserve character-by-character checking. Everything else can be read for sense.
If a whole passage is unusable, retyping it is faster than correcting word by word. Recognise that point early rather than fighting it.
Mixed forms
Forms combining printed labels with handwritten answers usually work well, because the printed part anchors the layout and the handwritten fields are short.
Checkboxes and ticks are not text and are frequently ignored or rendered as stray characters. Record those separately.