Fighting against the London System: D4, D5

Hello everyone !
I was looking at what my weak spots opening-repertoire-wise were.. And have found the London System to be particularily strong against myself.
I like to respond to it with d4 d5, as I expect a queen's gambit in which I could play the semi-slav.
However, I am filled with dread as they move their bishop out, for I have no particular preparation against such.
I would also clarify that, yes, I can look at videos online myself, there is no need to redirect me to them, I am looking for first-hand experience on what has worked for other players within these particular set of starting moves.

Good Question ... The London System is very popular at all levels.

I play

With the idea of playing Nf6, pawn to c5 and Nc6, from there look to play cxd4 or exchange the dark square bishops. I fight for control of e4, to prevent a unfavorable pawn push in the center.

All in all... (against people in my elo range) gives me a lot of play.

D-pawn variations are getting very popular now days (I just viewed a pod cast with one of the top trainers in the west. He stated, due to the modern chess engine, its extremely hard to get a thretical advantage in an opening. Gm's are now looking to play openings that have a lot of scope and depth, rather than look for sharp therectical advantages.

I think this has led to more and D-pawn variations at the upper levels.

There is no smoking gun for black...

The idea to play against London is to play solidly. White doesn't push for an advantage right out of opening, so black should just develop normally and look to control center, just look at key thematic tactics in middle game ... Otherwise it's a very solid opening, you fight for a long game

A few years ago the line I played against the London was this Qb6 one.

Most white players play 5. c3 there and the game has already equalized... but black has good activity, the line scores very well for black. However, this is the most common response to the London. I never liked how little effort the London player could put into their opening prep. I felt this Qb6 line wasn't surprising... there are infact a few London players who aren't dumb and know their opening past move 4, and so they'll play the correct move 4. Nd2 instead of 4. c3 there. I went into a phase of trying out other things...

I knew I didn't want to play 2... Nf6 since that's the most common move. And the 2... e6 > 3... Bd6 line, while it does neutralize the London bishop immediately, is also extremely uninteresting.

I tried this 2... Bf5 line -

I like that c4 there falls into an ugly position. Trouble is 2... Bf5 allows this other response where white has all the activity -

You can play that last position like a chigorin with 4... Nc6. Playing this requires some experience in chigorin structures. Black is scoring well there despite it not being objectively favorable... but ultimately I decided the level of effort required to play this way doesn't justify the payoff. It's still a fairly boring and now cramped position. 

So then I tried the Krause... the standard London move order became just bad, and not viable -

And for the accelerated London I could play this f6 line -

Now I'd really defeated the London... it either wasn't possible, or in the accelerated move order I usually get this fast kingside expansion and the position is quite favorable. There was only one issue...

Don't get me wrong, this is very much playable for black, and I played it for a while. 
The only issue with it, in my mind, is it requires prep to play. At some point I began to feel I was giving the London player more of my time / more of a game than they actually deserved. I did find a repertoire that was novel and interesting, and if I had the time to pour into my anti-Zuckertort repertoire I'd probably stick with the Krause.

But in the end I got caught up with other things besides chess... and so I returned to my original Qb6 move which, while it is boring... it really requires no prep on my part to play. It just equalizes the game and you play a game of chess, giving the London player no more time than they deserve.

TLDR, if you want to make the London player use their brain and you're willing to prep go with the Krause. If you want something simple that you can't really screw up, and which will allow you to focus on other things... go with Qb6.