The limitation with keyword and class code searching, of course, is finding the right keywords and class codes. Sometimes this is obvious - sometimes it is less obvious that we might want.
Luckily Ambercite Cluster Searching can help with this. Providing that you have reasonable patent number to start with, Cluster Searching can quickly find similar patents. Besides using these patents as results for your search, the titles of these patents can quickly suggest which keywords can be used to strengthen your conventional searching. Similarly looking at the top ranked patents can help suggest the likely class codes.
And this can be done very quickly, as discussed in the blog linked here