I'll show my walkthroughs for the first 2 puzzles, before posting the 3rd, which is the series finale...

(In the walkthroughs all cage sums are shown explicitly, as they're pretty obvious.)

Triple click below to see the walkthrough for Multiples Killer 1 which I wrote:(Notation: SYM=symmetrical property, AK=touchless)

6/3 @ r1c5={123} (NT @ c5,n2)

6/3 @ r2c2={123} (NT @ d\,w1)

24/3 @ r6c6={789} (NT @ d\,w4)

24/3 @ r7c5={789} (NT @ c5,n8)

SYM: r5c5=5 (NE @ d\/)

=> r46c5={46} (NP @ n5)

=> \19={46} (NP @ r159c159)

Now {46} @ r5 locked @ 12/3+18/3

SYM: each of 12/3 & 18/3 @ r5 can't have both of {46}

=> One of these 2 cages has 4, the other has 6

=> 12/3 @ r5c1 can't be {156|246|345}

=> 12/3 @ r5c1={147} (NT @ r5,n4)

SYM: 18/3 @ r5c7={369} (NT @ r5,n6)

=> r5c46={28} (NP @ n5)

Similar line of reasoning:

12/3 @ r6c4={147} (NT @ d/,w3)

18/3 @ r2c8={369} (NT @ d/,w2)

/19={28} (NP @ r159c159)

9 @ c6,n5 locked @ r46c6

6 @ r5,n6,r159c678 locked @ r5c78

4 @ d/,n7,w3 locked @ /78

=> 4 @ c1,n1 locked @ r123c1

=> 4 @ c4,n2,w1 locked @ r23c4

=> r123c6={578} (NT @ c6,n2)

AK: r2c7 can't have {578}

r456c6=[329]

=> r456c4=[187]

AK: r37c5=[28] (2 NE @ r234c159, 8 NE @ r678c159)

AK: r5c37=[46], r4c7 can't be 2

=> HS @ r4: r4c8=2

=> r6c789={145} (NT @ r6,n6)

AK: r7c8 can't have {145}

r46c5=[46]

6/3 @ r2c2=[231], 18/3 @ r2c8=[693]

12/3 @ r6c4=[714], 24/3 @ r6c6=[978]

=> r7c8=3

AK: r123c4=[946], r6c123=[382], r789c6=[461]

AK: r7c4+r8c3=[59]

AK: r4c3=5

All naked singles from here.

Eeeasy, peasy?

Just a brief entrée to get you warmed up on the

symmetry tricks...

Then along comes the main course:

Triple click below to see the super tricky walkthrough for Multiples Killer 2 which I wrote:(Notation: SYM=symmetrical property)

6/3 @ r1c5={123} (NT @ c5,n2)

24/3 @ r7c5={789} (NT @ c5,n8)

SYM: r5c5=5 (NE @ d\/)

=> r46c5={46} (NP @ c5,n5)

Now {46} @ r5 locked @ 18/3+12/3

SYM: each of 18/3 & 12/3 @ r5 can't have both of {46}

=> One of these 2 cages has 4, the other has 6

=> 18/3 @ r5c1 can't be {459|468|567}

=> 18/3 @ r5c1={369} (NT @ r5,n4)

SYM: 18/3 @ r5c7={147} (NT @ r5,n6)

=> r5c46={28} (NP @ n5)

9/3 @ /2 from {12346789}={126|234}=[{26}1|{24}3]

=> /23={24|26} (2 @ d/,n3,w2 locked)

21/3 @ /6 from {12346789}={489|678}=[7{68}|9{48}]

=> /78={48|68} (8 @ d/,n7,w3 locked)

/2378={2468} (NQ @ d/)

15/3 @ \2 & \8 from {12346789}={168|249|267|348}

=> 15/3 @ \2=[{68}1|{48}3|{26}7|{24}9]

=> 15/3 @ \8=[1{68}|3{48}|7{26}|9{24}]

=> \23={24|26|48|68}, \78={24|26|48|68}

=> \2378={2468} (NQ @ d\)

r19c19={1379} (NQ @ r159c159)

=> r19c5=[28], r5c19=[64]

=> 2 NE @ s2, 8 NE @ s8, 6 NE @ s4, 4 NE @ s6

=> r23c5={13} (NP @ r234c159), r78c5={79} (NP @ r678c159)

=> r5c23={39} (NP @ r159c234), r5c78={17} (NP @ r159c678)

1 @ n3 locked @ r1c9+r2c7+r3c8 (pointing @ r4c6)

=> 9/3 @ /2=[{24}3] (NT @ d/,w2; 4 @ n3 locked)

=> 21/3 @ /6=[7{68}] (NT @ d/,w3; 6 @ n7 locked)

1 @ n3,w2 locked @ r2c7+r3c8

=> /19=[91]

3 @ n1,w1 locked @ r2c3+r3c2

=> \19=[73]

HS @ s3: r4c3=7

HS @ s7: r6c7=3

HS @ n3: r1c8=3

HS @ n7: r9c2=7

1 @ r1,n1 locked @ r1c23

9 @ r9,n9 locked @ r9c78

2 @ n1,w1 locked @ r23c23

8 @ n9,w4 locked @ r78c78

Critical Step #1:

1 @ r4,w1 locked @ r4c24

15/3 @ \2=[{24}9|{68}1]

But \234+r4c2 can't be [{68}18] (all 4 cells @ w1)

=> r4c24 can't be [81]

=> r4c2 can't be 8

Tricky Symmetry Step #1:

2 @ r4 locked @ r4c19

SYM: r4c19 can't be {28}

=> r4c19 can't have 8

HS @ n4: r6c1=8

SYM: r4c9=2

=> r234c1={459} (NT @ c1,r234c159)

=> r46c5=[64] (6 NE @ r234c159)

6 @ r2 locked @ r2c236 (pointing @ r3c4)

4 @ r8 locked @ r8c478 (pointing @ r7c6)

6 @ n1,w1 locked @ r23c23

4 @ n9,w4 locked @ r78c78

Tricky Symmetry Step #2:

6 @ c4 locked @ r19c4

SYM: r19c4 can't be {46}

=> r19c4 can't have 4

4 @ c6 locked @ r19c6

SYM: r19c6 can't be {46}

=> r19c6 can't have 6

6 @ r1,s1 locked @ r1c47

4 @ r9,s9 locked @ r9c36

=> 15/3 @ \2=[429|681|861] (\2 can't be 2)

=> 15/3 @ \6=[186|924|942] (\8 can't be 8)

Tricky Symmetry Step #3:

r28c2 from {468}

SYM: r28c2 can't be {46}

=> 8 @ c2 locked @ r28c2

Critical Step #2:

r1c2+r23c1 from {1459} must have 1|4 (with 1 @ r1c2 only)

=> r24c2 can't be [41]

=> \234+r4c2 can't be [4291]

=> r4c2 can't be 1

HS @ r4: r4c4=1

15/3 @ \2: \23={68} (NP @ d\,n1,w1)

HS @ s9: r6c3=1

HS @ n4: r6c2=2

HS @ r3: r3c7=2

=> r7c7=4, SYM: r7c3=8

HS @ n7: r9c3=4

All naked singles from here.

The last dish, Multiples Killer 3, will come later, and by no means will it be a cheesecake or any other dessert!