Ok, here we go. I know makeup is quite a big thing in Australia, so here's what I would do.
Darken muzzle and carefully apply white makeup to make snip stand out more.
If you clip out the insides of your ears, apply dark makeup carefully into those too, but obviously not too far.
I would put some makeup around the eyes too. I would oil/highlight his chestnuts to darken them, and apply a clear highlighter to the sheath as well. Over here you can can get a clear highlighter that also acts as a fly repellent and sunscreen. Use that on his knees, hocks and lower legs, but not the white.
At every stage you use the makeup you need to dab on a small amount, then really blend it in. I would use predominantly red black, and then futher blend it with a clear highlighter, on the ears, around the eyes and around the muzzle.
Assuming he moves straight and correctly, I would put black polish on his feet rather than clear. It makes the socks more eye catching. If you trim the socks around the coronet band, it stops you getting black polish on white hairs.
Once everything is on, I would apply coatshine. With the makeup, remember that its easier to add more than to take it off. So do lots of practising, take photos after every few dabs and then see what looks best. If you keep standing back you'll be able to see what suits and what doesn't.