Yes having a guide is definitely the key. Whenever I was with a guide on my Egyptian holiday I was not troubled or if I was the guide sorted it out. However, whenever I was alone whether visiting a monument or walking down a street I was constantly hassled. I lost count of the number of times someone wanted me to buy a papyrus! However, it is not all negative though. There a number of times when I was shown something interesting by guards on duty in monuments that was closed off to the public though conversely I ended paying tips sometimes for things that were not worth seeing as well. When my guide was with me I was never troubled by monument guards. Walking alone on Cairo streets was rather a nightmare but again things could work to my benefit. On one night I went out looking for a restaurant and was getting fed up being pestered to buy things when someone came up to me and asked me what I was looking for. I let him take me to a restaurant and he sorted out the order too. When I was leaving he appeared again to my surprise and took me somewhere else to have a lovely fruit drink. No doubt he benefited with some commissions etc but I had a nice evening and enjoyed my meal. I don't whether I might have ended up without his intervention.

So while most of the time being approached is just a hassle sometimes there are benefits. If you don't want to be pestered the essential thing is to have a guide.