Setup Illustrator Document for Large Format Printer

Hello There!

I am Akalanka, I am fresher here, i need advice...

Basically I am design Billboards in Adobe Photoshop. but now i am doing billboards in Adobe Illustrator.
the Problem is. Document Size and export at correct Resolution to printer.
The Billboard Main Size is 20 feet x 19 feet, illustrator cannot create document Larger Than 227 inch.
so I decided to Make the 20 feet x 19 feet main board as Ratio 10 feet x 9.5 feet. but when send this size (10feet x 9.5feet) file into my Wide fromat printer Rip software and Scaled it up Main Size (20feet x 19feet), and print unfortunatly all text are Totaly Blured and Pixelated.
How can i Export it Correctly for Printer to Scale it up. Without Loosing Quality.
I heard there a trick to Rasterize Techince Before export. Can anyone guide me to Do it Correctly..
I hope you understand
Thank You