I’m no body-man, but POR15 is some wicked good stuff!

 

I use 3M two part self leveling in gutters. Just make a masking tape dam to keep it in the drip rail. For thick bodied I use the 3M two part thick bodied sealer.

Two part sealers are the way to go imho. No cracking down the road.

Don

 

X2

 

These absolutely work in all situations, I know for a fact, as I use them weekly. Will never crack or go bad.

 

I used this sealer in the gun.

Ultra-Flex Brushable Seam Sealer | Transtar Autobody Technologies (tat-co.com)
Ultra Flex Brushable Seam Sealer is a rapid curing, flexible seam sealer designed for all types of painted surfaces, bare metal and primed surfaces. It is resistant to weather exposure and temperature variations. Paintable and sandable. It remains flexible and seals wet or dry. Use to seal seams in floorpans, fire walls, truck seams, wheel wells, etc. Brush marks duplicate original factory finish. Skins in 5 minutes. Air drys in one hour.

APPEARANCE	Gray
SHELF LIFE	1 Year
VOC - REGULATORY	2.82#/gal (338 g/l)
VOC - ACTUAL	2.82#/gal (338 g/l)
DRY TO PAINT	30 minutes
WORK TIME	5 minutes
TDS NUMBER	325

 

Some seam sealers require you to buy a very expensive applicator gun. I chose my seam sealer because it requires only a standard caulk gun. I have a good caulk gun. It costs more the $2.00.

Eastwood sells a two-part self-leveling seam sealer. The plastic pointy tip mixes the two parts before it exits the chalk gun. It is good for certain areas. You mentioned the seam between the rocker and floor pan. Self-leveling is the best for this area. The blue stuff is the seam sealer.

It is also good for the joint between the tail panel and trunk pan.

Self leveling seam sealer flows into the joint. It fills the area so there are no air spaces between the seams. You can push the thick type of seam sealer into the crack with your finger, but there still might be an air space.

The thick seam sealer is good for vertical and sloping joints.

Notice the tape? I hate the way seam sealer looks. I mask off the area being seam sealed and apply the sealant. After a short while before it gets completely dry, I peel off the tape leaving a very thin line of seam sealer in the joint.
Here is a door edge being seam sealed.

I push the seam sealer in the joint with my finger the tape protects the surrounding area from looking like a compete mess. The black seam sealer is UPOL Tiger Seal. It is a 1K sealer that can be applied with a caulk gun.

Here are the joints seam sealed and after paint:

 

I have used Tigerseal 1k on a few jobs nearly 20 years ago on daily drivers and it has not failed or cracked. I use and stock SEM products primarily. One and two part. Seam sealers are easily spread in a driprail with a finger and come put perfect....even without self leveling sealer. Do it often and it is a cake walk.

You guys who do roofing or lightening rod protection ever use Geocell or M1? I have. Paintible and inexpensive. Flexible and long lasting. Good for a roofing company .... Good for a car that never sees the road. Guess I'm just lucky to have exposure to multiple industries.

No need for Eastwood. I have multiple local jobbers that deliver to my door the same day.