Using In Clause For a Large Text Matching Query

Hello all, my first post to the pgsql mailing list!

There may be a completely better way to do this; if so please help point 
me in the right direction!

What I'm trying to do is run a query to partially match 300+ text fields 
to a PG table of about 200,000 rows. The idea is to pull out a portion 
of text from the original text fields and do a partial text match on 
anything in my PG table containing that substring.

I liked the idea of using a where IN(group) to do my comparisons, as in

select col1 from table1 where col1 in ('text1','text2')

however, this requires an exact string match. Is there any way to do a 
substring match inside of my IN group? Or can anyone think of a better 
way to do something like this?

Heres an example of something of how I'd like this to work:

Portion of 300 Original Text fields:
"brown cat"
"green dog"

2 rows of 200k+ Database table:
"brown kitty"
"green doggy"

We can assume a certain portion of the text is included in the DB table, 
so I want to be able to do a substring match on "brown" and "green" and 
in this case return both "brown kitty", and "green doggy". However the 
problem is, if I run the query on each of my 300 rows to scan 200,000 
rows in my DB is entirely too slow. So I was hoping to use the IN clause 
to create an IN group of about 300 items to scan the DB once.

I hope this makes sense, but if anything sounds confusing please let me 
know, and I will be sure to clarify! Thanks for any help or direction 
anyone can provide!!

- Jason Farmer