I freshened up my 14ft aluminum last year. First I flipped the boat upside down then used a wire wheel to clean and prep every seam and area where I could see separation.
Then I used some painters tape and a friend's help and made two tape lines on either side of the seam. Once that was done I used 3M marine sealant in each seam and used my finger to smooth it out and press it in. After they were all done, I removed the tape and there was zero goopy mess around the seams. Nice and clean lines.
After that, I used the wire wheel to clean up the oxidized paint on the sides and repainted it with the same colour.
Doesn't leak at all now, and it looks amazing.
My 2 cents.