I've never bothered with seed sowing compost, considering that , naturally seeds would grow on whatever soil they landed on, rich or poor
If you can only get/have already, a course textured compost - you may be better off sieving the top layer, sowing the seeds onto that and then sieving a fine layer over the top, so the seed doesn't get swamped.
As a last resort sieve some garden soil and sterilise it in the microwave for a minute or so