I do agree that committed volunteers are much more important than simple cash in signature collection (look at the success of the Libertarian party in getting on the ballot in Texas for many years). I question whether it is more important in the general election, though.
To maintain ballot access, a party has to have a candidate get 5% of the vote in a statewide race. The Democratic Party typically doesn't field candidates for all of the seats on the Supreme Court or the Court of Criminal Appeals, and a Libertarian candidate will get 15-18% of the vote when running against an otherwise unopposed Republican.
In 2000, the only year the Green Party qualifed, their candidates received 7-9% of the vote in the judgeship races.
In 2002, the Democrats ran candidates for all the court seats, and both minor parties lost ballot access. The Libertarian Party, repetioned for access in 2004 and maintained it in that election.
In 2006, the Democrats only have candidates for 2 of 8 open court seats.
They qualified in 2000 as part of the effort to nominate Ralph Nader.