Your getting there.
Fenders are much more difficult, due to the thinness of the metal, so practice on some thin scrap metal. I did a front valance Shelby mod on my sons 65 Mustang, Lots of burn thru's. If that happens reduce the voltage and go back over it. Grind it clean and smooth and see where you have to fill in. Also Bondo works wonders.
Keep practicing. I find welding just varies form day to day at my skill level. Running a few beads on scrap metal before starting is always a good idea. It gets you back to looking at the puddle.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car