Fly considerably higher than 500-1000ft... have a target level, say 4000-4500 and stay within your band, use GPS and follow the track line, don't try too hard to fly the aircraft. Without a horizon, its easy to end up with PIO due to making tiny corrections all the time. Just relax and correct any deviations once get beyond limits you have set yourself (eg vsi 200ft/min - compass 10deg off course).
Remember the more height you have, the more time you have to manage an emergency, should one occur. Over water, your want all the time you can get.