If the car's never been clayed then the first clay will always be the hardest/longest. After that, if you keep on top of the car (ie clay and polish max twice a year), it will be a lot easier.
When I first clayed, I found I used a lot of lube too but now use much less - you get a feel for how much you need. Certainly never used more than 3/4 of a bottle. In future, you can use Bilt Hamber clays which need only water as lubrication. Personally, I use Dodo Juice Born Slippy which acts as lube and cleaner, though can be expensive.
You'll speed up as you continue detailing as you'll prepare everything beforehand and know what to do next without having to think about it much. My first detail took me all day. Most recently, I did a snowfoam/2BM wash/clay/hand cleanse/wax/windows/trim/wheels/tyres all in about 4-5 hours. I started at 6am that day!
Detailing is more difficult in winter due to shorter days and terrible conditions. This is why I did my last thorough detail back in September when the days were still relatively long. This weekend, I got the car out and went over it. Two hours to snowfoam, wash, dry and rewax, including getting equipment out and putting everything away.
Keep at it!
