I have two Lennox Furnaces (2005) with automatic pilot lights - one in the attic and one in the garage.

I am about to use flea bombs and wonder how to turn off the pilot lights (and then turn them back on again). The flea bomb instructions say to do this so there is not an explosion - but, my Lennox instructions say to NEVER manually turn on/off the pilot light.

How can I prepare my furnaces for the flea bombs?

Are these standing pilots, on all the time, or ones that light when the thermostat calls for heat? If the pilots stay on, you will just have to shut them off. If they only come on when the heat cycle starts, then they are already off most of the time. Just switch the thermostat to off so the furnaces can't come on.

I don't know how to tell if my pilot light is the kind that stays on all the time or not... should I turn my thermostat all the way down and then look to see? Will I be able to see my pilot light if it's on?

And if it's the kind that I just have to turn off - how do I do that?

Start by reading how to light a pilot light in the sticky at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html
If your gas valve doesn't look like the one there, and the little tube going into the furnace doesn't have a flame at the end of it, then your pilot light isn't on all the time. Just turn the furnace off and bombs away.

If you do have a pilot light that stays on, you should be able to turn it off anytime. Turn the knob from on to off. After the house clears out, follow the instruction in the sticky.