I had to rebuild my power steering pump on my UZZ31 and was advised by the rebuilder that the reservoir should be flushed with the installation of the rebuilt pump. Here's a video https://www.youtube.com/watch?v=7u6za7NxUJU
Also, as my seal on the reservoir was leaking I got a custom seal made by https://sealteam.com.au/ for $20. if you want to order one quote "MPN/RUBER LID SEAL" as they have saved the template design. The seal should also fit Supra and Landcruiser as they appear to be the same except for the mounting brackets.