Pingree Park Road is county road 63E, well marked and on all maps. There are disbursed sites for at least the first three or four miles. They are heavily used on weekends and expect constant dust from passing cars. About three miles up you can take a right on Crown Point Road for more sites.
Stove Prairie Road is mostly no camping and private land.
If you are up for some easy four-wheeling, take similarly named Pingree Hill Road (county road 69) north from Rustic. Take a left in about a mile, at a wide area, on Seven Mile "Road" (Forest Road 225,also county road 71B I think). The stream crossing is not deep right now and there are some sites. These continue for some miles but the four-wheeling gets more difficult.
That's about it for the whole Poudre Canyon.