Break the number x into chunks, where each chuck starts with a 0 and ends just before the next 0 (and must include some nonzero digits). Multiply each chunk by 8, and then add the chunks up.
For example, the first chunk is 0.1234567891. Multiply that by 8:
The second chunk is 01112131415161718192. Multiply that by 8:
Hence the first 31 digits (30 decimal places) of 8x is:
Now continue with the third chunk 022122232425262728293, fourth chunk 03132333435363738394, etc.