This is the way. Time yourself by hand. Automate. Use the saved time to automate further. Meet deadlines as if you were doing it by hand. Then during the inevitable crunch time you can miraculously come through. Each quarter, cut about 10% off the time you "need" to do automated tasks, showing constant improvement.

Lastly, always guard source code closely and be aware if coding on company time means they own that code. You can bring up that you think something can be automated, but this is a job they're gonna have to pay you extra for. Show a demo if you need to, but remember that coding automations isn't your job, so don't hand that over for free (payment in social capital depends on your job).