You can pass the cool.X parameters interactively via CGI when you run a query, so this can be a good way to test how different weightings will affect the result set.
Generally speaking tuning the ranking algorithm is the best way to get the best overall improvement in your result set because there is a much more rigourous process involved when determining the optimal ranking settings.
However if you do want to adjust the values manually adding the cool.X parameters will show you immediately how the results are affected.
So for the QIE example - once you have added the qie.cfg and reindexed you can run searches adding cool.4=X to the URL to see the effect of the QIE. e.g. http://mysite/s/search.html?collection=mycollection&query=searchterm&cool.4=0.7
Similarly you can add cool.68, mentioned in one of the other examples to the URL as well once the gscopes are set up in the index.