Insert Copied Cells multiple times, shift cell down

hi
i have data with up to thousands of rows down, there's a blank row in between them, and now i like to enter sub info using =formula in that blank rows, its going to be the same sub info for all line, but this sub info can go up to 1000 rows

at the moment i can copy this sub info from the 1st line and insert copied cell in the 2 blank row with shift cell down, no problem, works great but not so great if you have thousand of line to be inserted with this sub info, i'm talking about almost ten thousands, probably going to take over 3-6 months to do this,
can anyone please help me here

option that i thought might help: create enough space(if 900 rows needed than insert new 899 rows in between? 899 blank rows x lets say(1000 main info) so i can paste multiple times? that still going to take months

please help

everything from row 2 to row 29 is a sub info that need to be copy underneath main info

thank you thank you thank you