I'm sure you've had the experience of studying the form intensely for hours and then late on Friday it pours raining. You are sitting there with your form guide full of ticks and crosses and circled numbers and underlinings and question marks, and now it is absolutely hissing down outside, and you aren't sure - to bet , or not to bet, that is the question.
Well going back a few years - when it did used to rain ( - probably this applies to the the southern half of Australia only - ), when black clouds came over it caused kindergarten kids to run inside screaming, 2 y-o colts used to go berserk, and when footy players used to get muddy shorts, it was a chance to back the wet trackers. I didn't have much time to study form in those days, so in the interest of having a bet I used a very simple method of picking potential winners very quickly that was quite successful. This was a while ago so I have no records or stats, more of a perception that I generally ended in front.
Recently when I read the mechanical longshots selection thingo, principle of starting at the highest number and looking for "c d" form reminded me.
I used virtually the same idea but for heavy track days only. Rules are as follows.

Only applies when track is HEAVY.

Start at highest number (bottom weight) and highlight horse with WIN on heavy track.

A.If there is only one horse that qualifies on the set weight that is the selection.
B.If there are more than one horses on the same weight, make a selection based on your own experience of which is the best contender using performance on track, at the distance, barrier, jockey etc.
If you are left with two horses, consider backing both - or if more ignore the race.
Applying this to Flemington races tomorrow (Sat 6 May) I came up with the following :
from rule A
R1 #7 Speedy Rossa (showing $11)
R2 #6 Il Favorito (showing $17)
R3 #2 Alim (showing $15)

from rule B
after using some of the separation criteria mentioned above :

R4 #9 Reggie ($5.50) (Win percent 26%, #8 was 8%)
R5 NO BET - too many contenders
R6 #12 Jygah ($11) (#10 and #11 not done much at 1600)
R7 #13 Sensational Swing ($17) (#9 and #10 only won on slow)
R8 #8 Blue Collar Jack ($11) (#13 ave prz mny abt $3000 - outclassed,-#11 slow only).

No more rainy day blues

Cheers