I have an overactive letdown too, and I pop her off once I feel the letdown and catch the spraying milk in a burp rag or towel. Then I put her back on when the milk slows down. I have only recently stopped doing this (she's 4mo) because I noticed that she no longer gulps when eating, so I think she is handling it much better. In fact, I think now she prefers the fast letdown because she will fuss sometimes if the milk is taking a while to letdown.
It can be really frustrating (esp in the MOTN), and you will end up with BM on EVERYTHING! But it is something that I think most LOs get used to by 3-4 months.
Do you also have an oversupply? When I was out on maternity leave I had oversupply and the fast letdown. I had to go to block nursing for a while to get the supply under control, which did help a lot.