Hello. In video below I will show easy and non-risky method of ballasting turnouts. This method gives good results and is suitable for beginners and those modellers, who don't have large experience in ballasting. Ideal for ballasting complex turnouts (double slips and 3-way turnouts).
Also, if you need to ballast double slip using this method of ballasting, I recommend to pour glue to the point, shown on image below. Glue will flow under sleepers in all directions, and and the majority of ballast under double slip may be saturated from this single point.
Lastly, another two good videos about ballasting (this videos are not my): Ballasting process: How to change colour of ballast: