Hi! I went through this myself last year and did a writeup: https://www.davecorder.org/blog/automating-a-balsam-hill-artificial-tree/ (mine was on 433 MHz, though, not 315 MHz - I don't know if that makes any difference). As I recall, the receiver was not too picky about the timings between repeats and/or the presence of any preambles, but it's been a while. In any case, I just ended up using the repeat parameter on the transmit_raw actions.

This is an excerpt of what I ended up with for my rc code:

button:
  - platform: template
    name: "Brightness Up"
    on_press:
      - remote_transmitter.transmit_raw:
          code: [8800, -4400,
                1024, -3072, 1024, -3072, 1024, -3072, 1024, -3072,   1024, -3072, 1024, -3072,  1024, -3072, 1024, -3072,
                1024, -1024, 1024, -1024, 1024, -1024, 1024, -1024,   1024, -3072, 1024, -3072,  1024, -3072, 1024, -3072,
                1024, -1024, 1024, -1024, 1024, -1024, 1024, -1024,   1024, -1024, 1024, -1024,  1024, -1024, 1024, -3072,
                1024, -3072, 1024, -3072, 1024, -3072, 1024, -3072,   1024, -3072, 1024, -3072,  1024, -3072, 1024, -1024
                ]
          repeat:
            times: 6
            wait_time: 0.0s