This may not be what you are after but there are four main methods I use:
1) Application of 23.5 Carat Gold Leaf
2) Hand Painting in with either One Shot Metallic Gold (looks very good indeed, very close to a real gold look)
3) “Flooding” with metallic acrylic artists paint, there are many threads on this forum about filling engraving using acrylic
3) Masking before engraving and spray painting with a rattle can. Ensure your masking tape is well adhered and the adhesive in the tape will not be too affected by the solvents in the rattle can paint.
Having said all that, filling with Gold Leaf on laser engraved wood can be problematic due to the grain of the wood left from laser engraving - some woods are better than others.
Not sure if this was of use in your case.
60w EFI 6090 & 100w Z4 Reci 6090 G Weike Lasers, 4 X 4 CNC Router
CLTT using Oki C822dn & Adkins Press
Glass Sandblasting, Woodwork Shop, etc...
V Carve Pro v8 & Photo V Carve, Lasercut 5.3, Corel Draw 2017 on Windows 7 and iMac (via Parallels), etc