I generally give land to members of my dynasty. The more landed members in your dynasty and the higher their prestige the bigger the prestige bonus when you start a new king and the lower the probability that you'll lose(or that titles will pass out of your dynasty.
Generally my recipe is this: #1 Make sure all male members of dynasty have wives with high fertility. Alliances and titles are less important IMO than additional sons in the dynasty. #2 Make sure all female members of the dynasty are in matrilineal marriages. For members that aren't in your court recruit a courtier and then bribe your dynasty member to marry him. #3 Split the land you get evenly between male dynasty members and female members in matrilineal marriages. Even though they might not like you as much because they have indirect claims, they generally won't dislike you at the same time. #4 For vassals that are not dynasty members, induce them to rebel(levy their troops or make them court jester), or discover their plots with your spymaster. Then you can imprison them without penalty to other vassals. After they're in prison you can seize a title without penalty(Because they're a traitor), then give it to a dynasty member.

Other than that, try to make sure that your king's wife and you have high statesmanship so that you can manage a larger demense. And once you've got some decent troops you can seize a lot of land in holy wars without all the issues seizing claims etc. This is great land for buying off dynasty members that are threatening. Because of the debuff the land takes for a different religion conquer, your member won't be able to levy any troops on the land for 30 years. I once had a rebellion where the vassal could levy no troops at all.

Also ,I've found that you can win holy wars against some of those enemies with large coastlines even if you have fewer troops if you're tricky using ships. Basically, drop your troops in one end of their territory spread them out to the minimum needed to siege as many territories as possible. Hopefully you can win a couple sieges before the enemy 10k army makes it over your way. (You can place a couple ships further down the coast as scouts, or even use a council member.) Once the huge army makes it close, retreat to your ships. Don't fight it! Then use your ships to transport your army to other end of their coastline and start sieging over there. Rather than liberating the territories that you've already won, the enemy tends to walk all the way to where you started your new sieges. Since you used ships you can get there many months before them.

This is even easier if they're in another war, because their massed armies will tend to get distracted by the other enemy, giving you more time for conquering territory.

I generally give land to members of my dynasty. The more landed members in your dynasty and the higher their prestige the bigger the prestige bonus when you start a new king and the lower the probability that you'll lose(or that titles will pass out of your dynasty.
Generally my recipe is this:

1. Make sure all male members of dynasty have wives with high fertility. Alliances and titles are less important IMO than additional sons in the dynasty.
2. Make sure all female members of the dynasty are in matrilineal marriages. For members that aren't in your court recruit a courtier and then bribe your dynasty member to marry him.
3. Split the land you get evenly between male dynasty members and female members in matrilineal marriages. Even though they might not like you as much because they have indirect claims, they generally won't dislike you at the same time.
4. For vassals that are not dynasty members, induce them to rebel(levy their troops or make them court jester), or discover their plots with your spymaster. Then you can imprison them without penalty to other vassals. After they're in prison you can seize a title without penalty(Because they're a traitor), then give it to a dynasty member.

Other than that, try to make sure that your king's wife and you have high statesmanship so that you can manage a larger demense. And once you've got some decent troops you can seize a lot of land in holy wars without all the issues seizing claims etc. This is great land for buying off dynasty members that are threatening. Because of the debuff the land takes for a different religion conquer, your member won't be able to levy any troops on the land for 30 years. I once had a rebellion where the vassal could levy no troops at all.

Also ,I've found that you can win holy wars against some of those enemies with large coastlines even if you have fewer troops if you're tricky using ships. Basically, drop your troops in one end of their territory spread them out to the minimum needed to siege as many territories as possible. Hopefully you can win a couple sieges before the enemy 10k army makes it over your way. (You can place a couple ships further down the coast as scouts, or even use a council member.) Once the huge army makes it close, retreat to your ships. Don't fight it! Then use your ships to transport your army to other end of their coastline and start sieging over there. Rather than liberating the territories that you've already won, the enemy tends to walk all the way to where you started your new sieges. Since you used ships you can get there many months before them.

This is even easier if they're in another war, because their massed armies will tend to get distracted by the other enemy, giving you more time for conquering territory.