Using another program to resolve combat

[Suicide Junkie]

The stock game is quite biased towards easy glassing and hard capture.

In my mods, I like to give troops so many hitpoints, that they can absorb damage from orbital bombardments until the attacking ships run out of supply
Limiting the number of weapons which can hit planets is also good.

That way, it becomes easier and cheaper to let your troops do the shooting (since they have unlimited ammo) while your war fleet moves on to other tasks

PS:
Removing weapons from planets & weapon platforms is the key here...
Since the planets have no guns, the troop transports will be much more willing to assault the planet. Since your warships don't have to do any bombardment before the troops can land, a troop-landing strategy is much easier to achieve.