How to control multiple servo motors using two timers?
The high time used to command a hobby type servo motor is around 500us to 1500us.  The period is 20mS.  

Lets say you have 3 servoes connected to digital outputs I'll call S1,S2,S3.  You want the servo on time to be 0.8ms 1.2ms, 1.0mS.

Code will need to do the following:
0) At the start of each 20mS period:
1) Assert S1 signal high and wait for 0.8mS.  (Using a timer, or sleep, delay etc)
2) 0.8mS has elapsed, negate S1, and assert S2.  Wait 1.2mS.
3) Negate S2, assert S3 - Wait 1 mS.
4) Negate S3.  Wait the remainer of the 20mS.  (17mS)

If there are other ISRs operating on the machine, then the waits might no be accurate and you'll get some jitter.

A better way to implment this is in an ISR where on entry the signal assertion / negation is done - and the timer configured to generate the next ISR after the desired time.

The best way (zero jitter), if you have the hardware support is to use output compares.  Assuming the OCs have a high if less than compare mode then:

1) Program the 3 OCs compare values with the desired duration of each PWM.
2) Config the timer to wrap every 20mS
3) Enabled the OCs and start the timer.
4) When TCNT is &lt; the OC comparea value the output of each PWM will be high, and automatically go low when TCNT == the OC compare.