Hello Eric,
I’m not an expert on the relative merits of dish washing liquid I’m afraid!
However, there is some useful advice online (which you may have seen already).
Firstly, the ASO web page:
http://arksky.org/asoclean.htm
Secondly, there’s a very good Starizona video:
https://www.youtube.com/watch?v=loRrpM2MIdk
Also, there’s Ron Arbour’s approach using sellotape, as described in
the 2014 December Journal……only for the brave perhaps?!
Regards,
Martin