Respect the pyro, be sensible and it's safe
Use pyro from reputable suppliers
With a glance at my signature block you should notice my sponsor
Without blatent advertising they are well reputed and they have worked on recent European standards in the industry
4 seconds is plenty time, look, ignite, throw
(With smoke make that: look, ignite, wait for ignition sparks etc to be replaced by smoke, then throw)
Idealy I'd recommend wearing gloves playing and marshalling anyway. At the minimum a hit to a cold finger stings. Marshalling you don't get the painkilling effects of pumped adrenaline