This:
Regarding the challenge participation issue, I encourage ALL "rookies" to enter and enter
often. The challenge to copy a car that you might not even be interested in does wonders for
your abilities as a weatherer.
Followed by:
Life is short.
So, if it's short, why do a car you aren't interested in over the other dozen or so half done projects sitting around. I think everyone who's willing to take the time to do a weathering challange is the sort of person who's doing other things too, perhaps building a structure, or improving/building a layout, etc. So they wait until there's something of interest.
Now the topic itself of your reply, 'Life's too short to be "intimidated"' is good advice. If you're new and worried you won't "do well" figure that's exactly what's going to happen and do it anyway. At least some of the things you do will be right and the criticism from folks of what you've done wrong will help you do it better next time.
I liked that in some of the past challenges the persons who entered for that month decribed what they did, in reasonable detail. That was more common when there were in progress mid month postings, but I can understand why they were stopped.
Maybe along with submitting a month's entry the person needs to list out the steps they did, at least in general, ie:
"I started with a bunch of gold washes, each a bit more red than the last ..." not necessarily excrutiating detail like "First was a wash of 20% brandxxx coloryyy paint and 5% brandzzz colorxyz followed by a second wash of ..."