I use a 4gl, 3500psi with a variable pressure wand. Most contractors will agree use the least amount of pressure to do the job. It is a lot easier with a variable pressure wand, but by increasing orifice size of the tip will decrease your pressure. Distance from the surface is an art form to acquire, but you can bet that 12 or more inches is a place to start. I use a 25 and 40 degree tip depending on the nature of the surface I am cleaning. Keep checking in on your posts and others will respond, but the final answer comes from all the responses you will see. Put the replies to use and you will formulate what is best for you.
Reed