I don't have a handlebar-mouned bottle cage on the road bike as I do on the hybrid, and in the early stages I didn't need to have the weight of the Camel-Bak on me. Gunga Din wasn't around to fetch me my water, so I had to depend on myself. But learning how to remove/replace a water bottle from the down-tube cage was tricky.
Before I could even start with that, I needed to practice riding one-handed. Next, I practiced reaching down to touch the bottle while coasting, without actually taking the bottle out of its cage. That way, I could get used to the feel of how far I needed to reach in order to get said bottle. Next step, pull the bottle only part-way out of its cage, then push it back in. And, finally, actually pull the bottle out out the cage and get myself a drink.
Of course, getting the water bottle back into its cage while still rolling (OK, coasting) was a lot harder than taking it out. Any number of times I dropped the bottle and had to stop and get off of the bike to pick it up. Other times I had to grip the bottle's nozzle with my teeth for long enough to stop the bike and put the bottle back into its cage.
Even now, after nearly three years of using the road bike, I sometimes have trouble handling that water bottle. It's a good argument for using a Camel-Bak on long rides, in addition to the need to carry more water! On long rides, the bottle can be used for electrolyte drink.
There's a second bottle cage on the seat tube, but so far I don't try to get that bottle out while moving. That's for my spare water bottle, and if I need it, I stop and get it out. I very seldom set out on the road bike without that spare. I never know when I might need it.