I guess the sky monkeys have to spend more time getting rigged up in their mountaineering gear than they do actually making sure the job's done right, saw such a sight up the street today, you'd think he was scaling mount Everest...
To be fair, I'm pretty sure that such installers working on behalf of Sky have to take safety precautions are part of their working contract with them, not to mention a condition of their insurance. The use of body harnesses & hard hats might look a little silly, but I reckon looking silly is a small price to pay to not become another statistic alongside riggers, amateur radio operators, aerial installers etc. who've had "accidents" resulting in death, paralysis or some other injury, sometimes permenant, over the decades. While most enthuasist corners on the web and elsewhere will not usually tell you to go as far as always wearing an arrest harness, they will emphasise about taking firm precautions if you're more than a couple or so rungs on a ladder above the ground, which should either be properly secured and/or stabilised in the first place, as well as having the proper tools, checking before drilling etc. and importantly, realise that if you haven't got a head for heights then get someone whom knows what they're doing. I'm fortunate enough that my view of the satellite arc allows me to do my work at ground level in my back garden which allows me to easily access the dishes and outdoor distribution. The world does not need more Rod Hull's.
In any case, it only takes one or two seconds for an installer to pull down the shield, or maybe a couple of more seconds to fit in the rubber boot alternative (assuming they put it on the coax beforehand), there is really no excuse not to do it.
As for the diletric grease, it's often called silicone grease on this side of the Atlantic. Personally I've used the stuff that is generally used in the auto industry for several years without any issues and working well, though I seem to remember a while back here that in North America a specific type of diletric/silicone grease is recommended instead of those used for car wiring for some reason. All I can say is that the ordinary stuff I've bought on eBay from UK suppliers has not given me any issues. For my own "permenant" installations to the LNBs on dishes in the past I've used the standard screw-on f connector plugs on coax, drop a small bit of silicone grease inside the connector, screw on the connector to the LNB, wrap the connector with self-amalgamating tape, and then pull down any rain shield on the LNB and as long as it is done properly then it'll last a long time, with the F plugs looking like the day they were put on when you take them off. For my planned set up in 2020 however I do have some compression & crimp F plugs alongside the proper tools for them, as well as some rubber O-rings for plugs that don't have their own. But I must also say that in my experience looking at other's satellite installations locally (including some that are taken down after a good few years of service, sometimes 15 years or more), where conditions are usually damp and humidity often high, as long as you can prevent rainwater, sleet or snow from hitting the F plug which can seep moisture in through the gap between the body and the screw nut, or between the nut and the socket, then that is usually adequate for most domestic Sky & Freesat installations, highlighting the importance of pulling down those LNB rain shields! In other scenarios where you're working with finer signal margins or on commercial installations, then it makes more sense to ratchet up the waterproofing with self-amalgamating tape or good quality rubber boots/heatshrink, O-rings, silicone grease etc. to help keep not only moisture out but also limit water vapour to the nth degree.