You can encourage an earlier (but much smaller) crop from the indoor plants by stressing them. Allowing them to repeatedly almost dry out, and/or growing in smaller pots with less feed will cause earlier fruiting/ripening. Obviously, overdoing things is a danger, and you need to be on hand every day to continually monitor the plants. Once other plants are cropping, you can discard the forced ones.
Deliberate shading is not going to help. Tomatoes are evolved to grow in semi-tropical temperatures and light levels, so scrubbing the glass and cutting back any shading vegetation is a better strategy. Even clean glass cuts out some of the light, so I think it's a good idea to move plants outside during the day if there is a warm period early in the season when light levels are still low. White paint in the greenhouse interior, or temporary foil reflective surfaces placed under or around the plants can also help.
Removing a high proportion of the plant's leaves once a truss has formed will also encourage quicker ripening.
But as others have said, choosing early varieties will probably have as much effect as all of these points put together. I find Eastern European varieties are usually quick maturing, being suited to short Summers.
