Results depend on the preparation and effort you put into it.
Preferably use an appropriate paint for the material you are painting, and especially for goggles etc a paint that will have some flexibility
The goggles below were basic hard plastic, all dismantled, anything that didn't come off that was not to be painted was masked (eg the neck strap wrapped in a little newspaper and masking tape, and tape over the foam inside)
Rubbing down with some fine glass paper would give a better surface for the paint, this was not done to these goggles - but ensure it is clean, especially for the slightest greasy residue from paintballs
Paint choice - this was with paint that was in the shed, which was cheap car paint. Tan and green
First a basic undercoat Check recommendations for the colour scheme you use as to the right base coat - commonly white or grey. Obviously in this case I just started with the lightest of the colours and used tan as the base coat
Next these were just random costs of paint patterns
Some sprayed using masking by laying masking tape, with ripped edges
Some sprayed free hand
These give the different edging finishes with hard breaks between green and tan or soft blending between colours
Note for masking tape - look for 'low tack' tapes, which are designed as masking tape, avoid masking by using strong tapes such as gaffer tape/duct tape - it's not masking tape and will peel away the lower layers of paint
This was a quick paint of a spare pair of goggles. They have been used as loan goggles and lasted a number of years with minor flaking in places
Next the headshield, the same kind of preparation and in the back view you can see some of the lighter green
These are only used for carrying a high head camera (hence the mount on top)
Again this is random coats but mostly dark matt greens, in the photo is looks mostly green