You can use a dimmer to control your heat source, as long as you are monitoring the temps with an accurate thermometer.

You just need to manually dial the dimmer in to reduce the heat output to get desired temp.

I use a $30 ReptiTemp 500r thermometer. It has a temp probe you put on the heat source, and then you adjust the heat output on a slider. It will then shut on/off the heat source to maintain that range. A dimmer simply lowers the output power.

If it works for you, I would just use that. The important thing is that you have something on your heat source (UTH) to keep the temps from skyrocketing in the 100+ range. (i.e, having an uncontrolled UTH is bad. It will get extremely hot.)