The fastest way to fill 1,000 rows with the same plain text data is to import from a CSV file:
1. Create a CSV file with your plain text data in 1,000 rows
2. In Clay, click Actions > Import > Import Companies From a CSV
3. Upload your file or drag and drop it
4. Click Add to current table > Continue
5. Select the columns you want to add
6. Click Add to table
Alternatively, you can use Google Sheets with a webhook to send data row by row, though this is slower for large datasets.