The best thing I have found for heat is different bulbs. I currently have a 25 watt bulb in my DIY bator. For you I'd use 3 or 4 light bulbs. Start at 25 watts and increase wattage if it doesn't stabilize out to the correct temp when you test it.
Use a fan in your bator. Even office fans that are $12.99 work. Noisy, but they work. Always test your bator for 24 hours and make necessary adjustments, then test again before starting the incubation process.
I wish I had added a thermostat. I just built my bator, but a thermostat would help and really enhance my hatch rates. However I did not want to fork out $30 on something that costed less than $40 to make, and I wasn't comfortable with doing my own wiring.