Giving the bolts a spritz of penetrant ahead of time is a good idea. I always forget this.

I am just a DIYer and not being a working mechanic I never understood the idea of prying on a wrench. I recently did the engine mounts on my W202 and used this prying technique. You get a stubby wrench on the top bolt, put your pry bar perpendicular to the stubby and against something solid and pry. All you need is one good pry to break the bolt loose.