David
As CJ said muse is a version of alprostadil, it comes in a plastic applicator that you push about 50mm down the eye of the penis and then push a button on the end of the applcator, remove the applicator and rub the penis between the hands, all quite painless.
From the reports from guys on here I don't think muse is quite as effective as the injections.
Stimulation is still important.
Thanks Chris