Hi Colin,
Each of the methods you mention will work on their day. There are no hard and fast rules relating to fishing, and conditions will differ from day to day depending on a number of factors (weather, light, wind etc). As for when to fish buzzers, I would say they certainly could work from March onwards, as son as the water warms a smidgen. In Ireland what we call buzzers are known as Duck Flies and the locals certainly fish them from March onwards.
At this time of the year (June/July) it is always worth trying the static method, even trying some kind of strike indicator, because sometimes the takes may be difficult to spot. If you use a team of buzzers, try putting a quite large one on the point, size 10 or bigger.
Also, try the floating version like a Ginked up Shipman's Buzzer. Personally I don't think the floating method requires much consideration regarding the colour of the buzzer, black being the easiest to see if you're fishing in open water.
Finally you will see that there are a miriad of colours to choose from but Black, Red and Green will be your main ones.
Good luck.
Colin North