I started to use PCBs in 70s designing them with pencil and squared paper and etch them myself.
So I think I am experienced but only in 2 layer PCBs.
I use only my own (carefully managed) libraries and not to be productive (in sense to design fast) is the main reason. In most cases my designs go directly (with no prototype done) to small scale production (like 100+ pcs) and main reason for my libraries is to protect me from my own mistakes (like assigning wrong footprint to symbol).
Moving in 2017 to KiCad I have organised my libraries before I started to design first PCB so for example I have never even seen how assigning footprints for all schematic symbols looks as I have never done it.
May be it will be helpful what once I have written about my libraries structure:
Manually assembling SMD is simpler than THT. You need not to bend and cut the ends. You need not to continuously revert PCB. You just have everything at top of PCB. Down to 0603 I see no problem with it.
If you order single layer PCB in most cases they will do it by etching the second layer - does not make sense. The best is to use 2 layer PCB. If you assume that you have whole bottom GND then at any PCB place you have GND only one via from you. Having not to find at single layer PCB a place for GND traces helps.