In the non-RS Z there is no red warning light if the key has been in the lock for 24h, just the oil warning symbol in the display. If the filter is prefilled, after start the warning light/symbol goes away in seconds and if not, it can take up to a minute until the oil pressure is ok. Before the oil pressure is what it should be I would not rev the engine since I don't think higher rpm makes the oil pump work any harder or helps filling the filter faster, you'll just cause more load to a non lubricated engine. Prefilling is not needed nor recommended (but yes, I have done it once anyway). I'll stick to the Kawasaki OEM filters only. Everyone makes their own decisions but the OEM filter costs just 13,9 EUR and you could only save a few EURs using some cheapo filter so I don't see the point not using an OEM.