Flashing windows and doors

I have a number of windows and doors that I want to flash between the frames and sarking for a brick veneer home. I’m at frame stage.

Usually I’m used to the window manufacturer providing some flashing to the reveals then I tape that onto the sarking, however these windows are commercial grade, so they have come without flashing.

Any recommendations on what to do? I have about 150 lineal meters of window frames (top/sides) to flash. I could buy some butyl tape, but this gets expensive when need 150m. Are there other options?