There are three ways to protect yourself from radiation:

-Distance
-Barrier
-Shielding

Of these, distance is the best. Since the amount of radiatin that reaches you (assuming a sherical or point source) is inversly proportional to the square of your distance increase (going from 1 to two feet, doubling your distance, cuts radiation to a quarter. If you go from 1 to eight feet, you have only 1/64th of the original radiation to contend with, etc.), it is your best defense BY FAR. No pun intended.

Second: Barrier. This method prevents radioactive materials from coming into direct contact with you. Especially useful if you are in an affected area and plan to leave it, or in cases of high-alpha dust. Example: Plutonium. A five-gram chunk of plutonium will kill you within months, through cancer. ONE TENTH of a gram of plutonium, enhaled as micron-sized dust, kills you inside six hours by destroying all blood cells through radiation. Why? Alpha radiation has extremely short range, a piece of paper stops it. Barrier protection, such as full-body, gastight suits with independant air supply prevent and plutionium or other dust from getting dragged into safe zones, or from being inhaled or otherwise absorbed into the body, where they are most dangerous. This type of protection allows the user to shed any radioactive material on entering a safe zone. Suits should NOT be re-used, a decon shower should be taken after removing the suit, just in case.

Third: Shielding. The least practical method. To stop beta radiation, you'll need to lug around 2mm aluminium plates, all over your body. For gamma, try 15 centimeters of lead. For neutron radiation... find a lake about 20 meters deep. Live on the bottom. Shielding is only practical in shelters, where it must be combined with barrier methods (used on air intakes and locks) to be effective.

A note about indicators: If you really are close enough to a dirty bomb to need immediate treatment, go jump in front of a train. If you exhibit radiation poisoning, future cancer is as good as guaranteed.

If you don't get rad poisoning, someone (the authorities) will soon (two-digit minutes) realize what that bomb was, and shove everyone in the area through emergency decon.

Thus: Indicators are relatively useless, TBH.

In a Dirty Bomb (or other NBC) scenario, I'd make tracks for the fire station, gear up, and head out with the NBC detection/Decon team. Best way to do it really.