I don't do that anymore. I try to push estimates as high as possible and then collaboratively cut down on requirements/promises/features to match an expected (time) budget.
This often leads to more pragmatic work items and sensible prioritization from the start. And it is an opportunity for general communication and understanding the value of things.
A lot of the time when you are working the delays aren't just the uncertainty of an individual task; it's that you're working on several projects at once, you're attending meetings, etc, so that you might only average 2 hours / day working on a particular task or you might not be able to start a task for several weeks (depending on whether you work sequentially or in parallel).
You still need a realistic, achievable estimate for that first time, in case management calls your bluff, but distinguishing between "the amount of effort this will take" and "how long it will be before it is complete" can help set realistic expectations while making it harder for management to mistakenly think you need two months to complete a task that could be done in two weeks.