I have some experience with solo games but, while I've read DW, I haven't played it.
That said, in a solo game I find that I need to bring my A game as a GM. In a traditional group, if you need a minute to think, you can often toss a decision point in front of the players and buy yourself a moment while they discuss. In a solo game, the only person the player can discuss things with is you, so that doesn't work.
That leads into my next suggestion which is to be very clear with your descriptions and don't hesitate to clarify (especially if the player seems like they might have gotten the wrong idea). In a group, other players will often course correct if someone misheard something or makes a false assumption. In solo play, that relies entirely on the GM.
Finally, I've found that the solo game tends to work best with one or more NPCs in the party. We tend to have the player run these NPCs and share RP duties between GM and player (usually the GM RPs the NPC, but if the GM is busy running other NPCs and the player feels their NPC should speak up, they are free to do so).
This is for multiple reasons. Firstly, it gives the player ways to bounce ideas off the GM while remaining in character.
Secondly, solo PCs are incredibly fragile. The party dynamic allows other PCs to save a PC who goes down. A truly solo PC is often at the mercy of the vagaries of the dice (although this is less of an issue in DW than D&D, since the GM is often able to interpret failures in less game ending ways).
Lastly, it enables intra party chatter, which is simply enjoyable. Being the solo tough guy can be fun, but it gets old after a while. It's more fun to be able to share victory with stalwart companions that you've grown attached to. (That's been my experience at any rate.)
