I use a hand held propane bottle that is cheap and easy. I would never do this around plants or tight areas. In gravel walkways, driveways and patios...sure. I dump decomposed organic matter between my plants on top of the soil. That kills or reduces vigor of any weed. The cool thing is that decomposed organic matter also feeds the soil, enhancing the bio-ta of your soil...which is eating the decomposed organic matter taking it back into the soil profile (4 -6") pooping it out and mixing organic matter aerating the soil FOR YOU.
This 'weed worry thing' in my mind and experience a waste of energy. In my gardens weeding is like...well like less than one percent of all my efforts. I happen to be the laziest gardener. If more energy is required then I must be doing something wrong to create more work.
Flame works well on those large areas but a gas powered blower does even better. To go over those areas once per week at the most blows out the seeds that have been imported by birds or wind. I've never had to 'pull weeds' as a chore. I pull a weed here and there, how could one not? I never allow a weed (plant out of place) go to seed. I weed wack or cover tiny germinated weeds ASAP.
Putting decomposed organic matter ON TOP of weeds, even large weeds, is probably the most effective thing I do then it is starving them out by weed wacking the photosynthetic growth off.
Maybe I am weird but I LOVE pulling out weeds, making piles of them to put in my compost piles. Always before they go to seed.