i would wait till you've mowed the existing grass at least 3 times then....
if you live in a climate that has winters, wait till the fall.
if not, figure out when the best month to seed is.
then cut your existing grass short, then use an aerator, then yes, a slit
seeder will do the job. keep it watered as best you can.

"John Murphy" wrote in message
...
I seeded my lawn about 14000sf three weeks ago we got a severe
thunderstorm
two days later washing out much of it. I continued to water to see what
would happen. Now I have a lawn that is very maze like patterened and
blotchy about 40% grass but very nice where it came up dense.

What I am wondering is can I use a Slit Seeder to overseed/reseed the lawn
without doing alot of damage to the good grass that has come in.

Thanks
jm